diff --git a/docs/source/run/parameters.rst b/docs/source/run/parameters.rst
index 501e7b6ea1..d3bd9555b5 100644
--- a/docs/source/run/parameters.rst
+++ b/docs/source/run/parameters.rst
@@ -1056,9 +1056,14 @@ There are different types of diagnostics in HiPACE++. The standard diagnostics a
 in-situ diagnostics allow for fast analysis of large beams or the plasma particles.
 Please make sure to always clear or rename the output folder before running a new simulation to avoid mixing data from different runs.
 
-* ``diagnostic.output_period`` (`integer`) optional (default `0`)
+* ``diagnostic.output_period`` (`integer` or `string`) optional (default `0`)
     Output period for standard beam and field diagnostics. Field or beam specific diagnostics can overwrite this parameter.
-    No output is given for ``diagnostic.output_period = 0``.
+    Diagnostic output is written to file when the current time step is a multiple of the
+    output period. For ``diagnostic.output_period = 0`` no output is given,
+    while ``diagnostic.output_period = 1`` always produces output. The output period can also
+    be a function of ``current_step`` and ``current_time`` to have finer control of when output
+    should be written. Examples of how to use this can be found
+    `here <https://github.com/Hi-PACE/hipace/pull/1334>`__.
 
 * ``hipace.output_folder`` (`string`) optional (default ``"diags"``)
     Set the output path of diagnostic data. By default all types of diagnostics will output
@@ -1075,9 +1080,10 @@ Please make sure to always clear or rename the output folder before running a ne
 Beam diagnostics
 ^^^^^^^^^^^^^^^^
 
-* ``diagnostic.beam_output_period`` (`integer`) optional (default `0`)
+* ``diagnostic.beam_output_period`` (`integer` or `string`) optional (default `0`)
     Output period for the beam. No output is given for ``diagnostic.beam_output_period = 0``.
     If ``diagnostic.output_period`` is defined, that value is used as the default for this.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 * ``diagnostic.beam_data`` (`string`) optional (default `all`)
     Names of the beams written to file, separated by a space. The beam names need to be ``all``,
@@ -1100,9 +1106,10 @@ Field diagnostics
     If ``<diag name>`` is equal to ``lev0 lev1 lev2 laser_diag``, the default for this parameter
     becomes ``level_0 level_1 level_2 laser`` respectively.
 
-* ``<diag name>.output_period`` (`integer`) optional (default `0`)
+* ``<diag name>.output_period`` (`integer` or `string`) optional (default `0`)
     Output period for fields. No output is given for ``<diag name>.output_period = 0``.
     If ``diagnostic.output_period`` is defined, that value is used as the default for this.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 * ``<diag name> or diagnostic.diag_type`` (`string`)
     Type of field output. Available options are `xyz`, `xz`, `yz` and `xy_integrated`.
@@ -1218,8 +1225,9 @@ Usage example:
     ir.time, ir.zeta # get metadata needed for plotting
 
 
-* ``<beam name> or beams.insitu_period`` (`int`) optional (default ``0``)
+* ``<beam name> or beams.insitu_period`` (`integer` or `string`) optional (default ``0``)
     Period of the beam in-situ diagnostics. `0` means no beam in-situ diagnostics.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 * ``<beam name> or beams.insitu_file_prefix`` (`string`) optional (default ``"<hipace.output_folder>/insitu"``)
     Path of the beam in-situ output. Must not be the same as `hipace.file_prefix`.
@@ -1228,8 +1236,9 @@ Usage example:
     Maximum radius ``<beam name>.insitu_radius`` :math:`= \sqrt{x^2 + y^2}` within which particles are
     used for the calculation of the insitu diagnostics.
 
-* ``<plasma name> or plasmas.insitu_period`` (`int`) optional (default ``0``)
+* ``<plasma name> or plasmas.insitu_period`` (`integer` or `string`) optional (default ``0``)
     Period of the plasma in-situ diagnostics. `0` means no plasma in-situ diagnostics.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 * ``<plasma name> or plasmas.insitu_file_prefix`` (`string`) optional (default ``"<hipace.output_folder>/insitu"``)
     Path of the plasma in-situ output. Must not be the same as `hipace.file_prefix`.
@@ -1238,17 +1247,19 @@ Usage example:
     Maximum radius ``<plasma name>.insitu_radius`` :math:`= \sqrt{x^2 + y^2}` within which particles are
     used for the calculation of the insitu diagnostics.
 
-* ``fields.insitu_period`` (`int`) optional (default ``0``)
+* ``fields.insitu_period`` (`integer` or `string`) optional (default ``0``)
     Period of the field in-situ diagnostics. `0` means no field in-situ diagnostics.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 * ``fields.insitu_file_prefix`` (`string`) optional (default ``"<hipace.output_folder>/insitu"``)
     Path of the field in-situ output. Must not be the same as `hipace.file_prefix`.
 
-* ``lasers.insitu_period`` (`int`) optional (default ``0``)
+* ``lasers.insitu_period`` (`integer` or `string`) optional (default ``0``)
     Period of the laser in-situ diagnostics. `0` means no laser in-situ diagnostics.
 
 * ``lasers.insitu_file_prefix`` (`string`) optional (default ``"<hipace.output_folder>/insitu"``)
     Path of the laser in-situ output. Must not be the same as `hipace.file_prefix`.
+    See the documentation of ``diagnostic.output_period`` for more details.
 
 Additional physics
 ------------------
diff --git a/src/diagnostics/Diagnostic.H b/src/diagnostics/Diagnostic.H
index 1e97234ee8..14872468ae 100644
--- a/src/diagnostics/Diagnostic.H
+++ b/src/diagnostics/Diagnostic.H
@@ -46,7 +46,7 @@ struct FieldDiagnosticData
     bool m_has_field; /**< if there is field output to write */
     /** Number of iterations between consecutive output dumps.
      * Default is 0, meaning no output */
-    int m_output_period = 0;
+    utils::DiagPeriod m_output_period = "0";
 };
 
 
@@ -80,9 +80,8 @@ public:
                          int output_step, int max_step,
                          amrex::Real output_time, amrex::Real max_time)
     {
-        return  (fd.m_nfields > 0) &&
-            utils::doDiagnostics(fd.m_output_period, output_step, max_step,
-                            output_time, max_time);
+        return (fd.m_nfields > 0) &&
+            fd.m_output_period.doDiagnostics(output_step, max_step, output_time, max_time);
     }
 
     /** \brief determines if any field diagnostic has any output on in this time step
@@ -114,8 +113,7 @@ public:
                         amrex::Real output_time, amrex::Real max_time) const
     {
         return m_output_beam_names.size() > 0 &&
-            utils::doDiagnostics(m_beam_output_period, output_step, max_step,
-                            output_time, max_time);
+            m_beam_output_period.doDiagnostics(output_step, max_step, output_time, max_time);
     }
 
     /** \brief determines if any field or beam diagnostic has any output on in this time step
@@ -173,7 +171,7 @@ private:
     amrex::Vector<std::string> m_output_beam_names; /**< Component names to Write to output file */
     /** Number of iterations between consecutive output dumps.
      * Default is 0, meaning no output */
-    int m_beam_output_period = 0;
+    utils::DiagPeriod m_beam_output_period = "0";
     amrex::Vector<FieldDiagnosticData> m_field_data; /**< individual field diag data */
     bool m_initialized = false; /**< if this object is fully initialized */
 };
diff --git a/src/diagnostics/Diagnostic.cpp b/src/diagnostics/Diagnostic.cpp
index e8f331a0bb..a41ddef91a 100644
--- a/src/diagnostics/Diagnostic.cpp
+++ b/src/diagnostics/Diagnostic.cpp
@@ -76,16 +76,18 @@ Diagnostic::ReadParameters (int nlev, bool use_laser)
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE( fd.m_diag_coarsen.min() >= 1,
             "Coarsening ratio must be >= 1");
 
-        queryWithParser(pph, "output_period", fd.m_output_period);
-        queryWithParserAlt(pp, "output_period", fd.m_output_period, ppd);
+        queryWithParser(pph, "output_period", fd.m_output_period.m_func_str);
+        queryWithParserAlt(pp, "output_period", fd.m_output_period.m_func_str, ppd);
+        fd.m_output_period.compile();
     }
 
-    if (queryWithParser(pph, "output_period", m_beam_output_period)) {
+    if (queryWithParser(pph, "output_period", m_beam_output_period.m_func_str)) {
         amrex::Print() << "WARNING: 'hipace.output_period' is deprecated! "
             "Use 'diagnostic.output_period' instead!\n";
     }
-    queryWithParser(ppd, "output_period", m_beam_output_period);
-    queryWithParser(ppd, "beam_output_period", m_beam_output_period);
+    queryWithParser(ppd, "output_period", m_beam_output_period.m_func_str);
+    queryWithParser(ppd, "beam_output_period", m_beam_output_period.m_func_str);
+    m_beam_output_period.compile();
 }
 
 bool
diff --git a/src/fields/Fields.H b/src/fields/Fields.H
index e9d980a0b2..51c9b8179c 100644
--- a/src/fields/Fields.H
+++ b/src/fields/Fields.H
@@ -13,6 +13,7 @@
 #include "diagnostics/Diagnostic.H"
 #include "laser/MultiLaser.H"
 #include "utils/GPUUtil.H"
+#include "utils/IOUtil.H"
 
 #include <AMReX_MultiFab.H>
 #include <AMReX_Vector.H>
@@ -475,7 +476,7 @@ private:
     static constexpr int m_insitu_nrp = 10;
     /** How often the insitu field diagnostics should be computed and written
      * Default is 0, meaning no output */
-    int m_insitu_period {0};
+    utils::DiagPeriod m_insitu_period {"0"};
     /** All per-slice real field properties */
     amrex::Vector<amrex::Real> m_insitu_rdata;
     /** Sum of all per-slice real field properties */
diff --git a/src/fields/Fields.cpp b/src/fields/Fields.cpp
index 4eb0208938..ae9cc83977 100644
--- a/src/fields/Fields.cpp
+++ b/src/fields/Fields.cpp
@@ -34,7 +34,8 @@ Fields::ReadParameters (const int nlev)
 
     amrex::ParmParse ppf("fields");
     DeprecatedInput("fields", "do_dirichlet_poisson", "poisson_solver", "");
-    queryWithParser(ppf, "insitu_period", m_insitu_period);
+    queryWithParser(ppf, "insitu_period", m_insitu_period.m_func_str);
+    m_insitu_period.compile();
     m_insitu_file_prefix = Hipace::m_output_folder + "/insitu";
     const bool set_file_prefix = queryWithParser(ppf, "insitu_file_prefix", m_insitu_file_prefix);
     if (set_file_prefix) {
@@ -246,7 +247,7 @@ Fields::AllocData (
             "'FFTDirichletQuick', 'FFTPeriodic' or 'MGDirichlet'");
     }
 
-    if (lev == 0 && m_insitu_period > 0) {
+    if (lev == 0 && m_insitu_period.isNonZero()) {
 #ifdef HIPACE_USE_OPENPMD
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE(m_insitu_file_prefix !=
             Hipace::GetInstance().m_openpmd_writer.m_file_prefix,
@@ -1355,7 +1356,7 @@ void
 Fields::InSituComputeDiags (int step, amrex::Real time, int islice, const amrex::Geometry& geom3D,
                             int max_step, amrex::Real max_time)
 {
-    if (!utils::doDiagnostics(m_insitu_period, step, max_step, time, max_time)) return;
+    if (!m_insitu_period.doDiagnostics(step, max_step, time, max_time)) return;
     HIPACE_PROFILE("Fields::InSituComputeDiags()");
 
     using namespace amrex::literals;
@@ -1416,7 +1417,7 @@ void
 Fields::InSituWriteToFile (int step, amrex::Real time, const amrex::Geometry& geom3D,
                            int max_step, amrex::Real max_time)
 {
-    if (!utils::doDiagnostics(m_insitu_period, step, max_step, time, max_time)) return;
+    if (!m_insitu_period.doDiagnostics(step, max_step, time, max_time)) return;
     HIPACE_PROFILE("Fields::InSituWriteToFile()");
 
 #ifdef HIPACE_USE_OPENPMD
diff --git a/src/laser/MultiLaser.H b/src/laser/MultiLaser.H
index e4a7aa158d..e8f2fadd19 100644
--- a/src/laser/MultiLaser.H
+++ b/src/laser/MultiLaser.H
@@ -13,6 +13,7 @@
 #include "Laser.H"
 #include "mg_solver/HpMultiGrid.H"
 #include "fields/fft_poisson_solver/fft/AnyFFT.H"
+#include "utils/IOUtil.H"
 
 #include <AMReX_MultiFab.H>
 #include <AMReX_Vector.H>
@@ -244,7 +245,7 @@ private:
     static constexpr int m_insitu_ncp = 1;
     /** How often the insitu laser diagnostics should be computed and written
      * Default is 0, meaning no output */
-    int m_insitu_period {0};
+    utils::DiagPeriod m_insitu_period {"0"};
     /** All per-slice real laser properties */
     amrex::Vector<amrex::Real> m_insitu_rdata;
     /** Sum of all per-slice real laser properties */
diff --git a/src/laser/MultiLaser.cpp b/src/laser/MultiLaser.cpp
index 900e0420ff..94d0b40a2f 100644
--- a/src/laser/MultiLaser.cpp
+++ b/src/laser/MultiLaser.cpp
@@ -63,7 +63,8 @@ MultiLaser::ReadParameters ()
         "if necessary, 'lasers.MG_tolerance_rel = 1e-7'. "
         "If for some reason you need to use the FFT-based solver plase open an issue on Github");
 
-    queryWithParser(pp, "insitu_period", m_insitu_period);
+    queryWithParser(pp, "insitu_period", m_insitu_period.m_func_str);
+    m_insitu_period.compile();
     m_insitu_file_prefix = Hipace::m_output_folder + "/insitu";
     const bool set_file_prefix = queryWithParser(pp, "insitu_file_prefix", m_insitu_file_prefix);
     if (set_file_prefix) {
@@ -193,7 +194,7 @@ MultiLaser::InitData ()
         m_rhs_mg.resize(amrex::grow(m_slice_box, amrex::IntVect{1, 1, 0}), 2, amrex::The_Arena());
     }
 
-    if (m_insitu_period > 0) {
+    if (m_insitu_period.isNonZero()) {
 #ifdef HIPACE_USE_OPENPMD
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE(m_insitu_file_prefix !=
             Hipace::GetInstance().m_openpmd_writer.m_file_prefix,
@@ -1055,7 +1056,7 @@ MultiLaser::InSituComputeDiags (int step, amrex::Real time, int islice,
                                 int max_step, amrex::Real max_time)
 {
     if (!UseLaser(islice)) return;
-    if (!utils::doDiagnostics(m_insitu_period, step, max_step, time, max_time)) return;
+    if (!m_insitu_period.doDiagnostics(step, max_step, time, max_time)) return;
     HIPACE_PROFILE("MultiLaser::InSituComputeDiags()");
 
     using namespace amrex::literals;
@@ -1144,7 +1145,7 @@ void
 MultiLaser::InSituWriteToFile (int step, amrex::Real time, int max_step, amrex::Real max_time)
 {
     if (!m_use_laser) return;
-    if (!utils::doDiagnostics(m_insitu_period, step, max_step, time, max_time)) return;
+    if (!m_insitu_period.doDiagnostics(step, max_step, time, max_time)) return;
     HIPACE_PROFILE("MultiLaser::InSituWriteToFile()");
 
 #ifdef HIPACE_USE_OPENPMD
diff --git a/src/particles/beam/BeamParticleContainer.H b/src/particles/beam/BeamParticleContainer.H
index c1371e3355..62b9575ed9 100644
--- a/src/particles/beam/BeamParticleContainer.H
+++ b/src/particles/beam/BeamParticleContainer.H
@@ -12,6 +12,7 @@
 #include "particles/profiles/GetInitialDensity.H"
 #include "particles/profiles/GetInitialMomentum.H"
 #include "utils/Parser.H"
+#include "utils/IOUtil.H"
 #include "particles/sorting/BoxSort.H"
 #include <AMReX_AmrParticles.H>
 #include <AMReX_Particles.H>
@@ -229,7 +230,7 @@ public:
     bool m_initialize_on_cpu {false};
     /** How often the insitu beam diagnostics should be computed and written
      * Default is 0, meaning no output */
-    int m_insitu_period {0};
+    utils::DiagPeriod m_insitu_period {"0"};
     /** Whether external fields should be used for this beam */
     bool m_use_external_fields = false;
     /** External field functions for Ex Ey Ez Bx By Bz */
diff --git a/src/particles/beam/BeamParticleContainer.cpp b/src/particles/beam/BeamParticleContainer.cpp
index 70d4f43b30..7f74fba361 100644
--- a/src/particles/beam/BeamParticleContainer.cpp
+++ b/src/particles/beam/BeamParticleContainer.cpp
@@ -59,7 +59,8 @@ BeamParticleContainer::ReadParameters ()
     queryWithParser(pp, "do_z_push", m_do_z_push);
     queryWithParserAlt(pp, "do_push", m_do_push, pp_alt);
     queryWithParserAlt(pp, "do_radiation_reaction", m_do_radiation_reaction, pp_alt);
-    queryWithParserAlt(pp, "insitu_period", m_insitu_period, pp_alt);
+    queryWithParserAlt(pp, "insitu_period", m_insitu_period.m_func_str, pp_alt);
+    m_insitu_period.compile();
     m_insitu_file_prefix = Hipace::m_output_folder + "/insitu";
     const bool set_file_prefix =
         queryWithParserAlt(pp, "insitu_file_prefix", m_insitu_file_prefix, pp_alt);
@@ -306,7 +307,7 @@ BeamParticleContainer::InitData (const amrex::Geometry& geom)
                              << "' will be initialized with no particles!\n";
     }
 
-    if (m_insitu_period > 0) {
+    if (m_insitu_period.isNonZero()) {
 #ifdef HIPACE_USE_OPENPMD
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE(m_insitu_file_prefix !=
             Hipace::GetInstance().m_openpmd_writer.m_file_prefix,
diff --git a/src/particles/beam/MultiBeam.cpp b/src/particles/beam/MultiBeam.cpp
index c2da13272a..6a8fd56ab7 100644
--- a/src/particles/beam/MultiBeam.cpp
+++ b/src/particles/beam/MultiBeam.cpp
@@ -96,7 +96,7 @@ MultiBeam::InSituComputeDiags (int step, int islice,
                                amrex::Real max_time)
 {
     for (auto& beam : m_all_beams) {
-        if (utils::doDiagnostics(beam.m_insitu_period, step, max_step, physical_time, max_time)) {
+        if (beam.m_insitu_period.doDiagnostics(step, max_step, physical_time, max_time)) {
             beam.InSituComputeDiags(islice);
         }
     }
@@ -107,7 +107,7 @@ MultiBeam::InSituWriteToFile (int step, amrex::Real time, const amrex::Geometry&
                               int max_step, amrex::Real max_time)
 {
     for (auto& beam : m_all_beams) {
-        if (utils::doDiagnostics(beam.m_insitu_period, step, max_step, time, max_time)) {
+        if (beam.m_insitu_period.doDiagnostics(step, max_step, time, max_time)) {
             beam.InSituWriteToFile(step, time, geom);
         }
     }
diff --git a/src/particles/plasma/MultiPlasma.cpp b/src/particles/plasma/MultiPlasma.cpp
index b3ca731f7e..fa689dc88b 100644
--- a/src/particles/plasma/MultiPlasma.cpp
+++ b/src/particles/plasma/MultiPlasma.cpp
@@ -183,8 +183,7 @@ MultiPlasma::InSituComputeDiags (int step, int islice, int max_step,
                                 amrex::Real physical_time, amrex::Real max_time)
 {
     for (auto& plasma : m_all_plasmas) {
-        if (utils::doDiagnostics(plasma.m_insitu_period, step,
-                            max_step, physical_time, max_time)) {
+        if (plasma.m_insitu_period.doDiagnostics(step, max_step, physical_time, max_time)) {
             plasma.InSituComputeDiags(islice);
         }
     }
@@ -195,8 +194,7 @@ MultiPlasma::InSituWriteToFile (int step, amrex::Real time, const amrex::Geometr
                                 int max_step, amrex::Real max_time)
 {
     for (auto& plasma : m_all_plasmas) {
-        if (utils::doDiagnostics(plasma.m_insitu_period, step,
-                            max_step, time, max_time)) {
+        if (plasma.m_insitu_period.doDiagnostics(step, max_step, time, max_time)) {
             plasma.InSituWriteToFile(step, time, geom);
         }
     }
diff --git a/src/particles/plasma/PlasmaParticleContainer.H b/src/particles/plasma/PlasmaParticleContainer.H
index ca942aab7b..cfd61aef13 100644
--- a/src/particles/plasma/PlasmaParticleContainer.H
+++ b/src/particles/plasma/PlasmaParticleContainer.H
@@ -12,6 +12,7 @@
 #include "fields/Fields.H"
 #include "utils/Parser.H"
 #include "utils/GPUUtil.H"
+#include "utils/IOUtil.H"
 #include "particles/profiles/GetInitialDensity.H"
 #include <AMReX_AmrParticles.H>
 #include <AMReX_Particles.H>
@@ -304,7 +305,7 @@ public:
 
     /** How often the insitu plasma diagnostics should be computed and written
      * Default is 0, meaning no output */
-    int m_insitu_period {0};
+    utils::DiagPeriod m_insitu_period {"0"};
 private:
     std::string m_name; /**< name of the species */
     int m_nslices; /**< number of z slices of the domain */
diff --git a/src/particles/plasma/PlasmaParticleContainer.cpp b/src/particles/plasma/PlasmaParticleContainer.cpp
index a009e06d31..0470d4f4e1 100644
--- a/src/particles/plasma/PlasmaParticleContainer.cpp
+++ b/src/particles/plasma/PlasmaParticleContainer.cpp
@@ -166,7 +166,8 @@ PlasmaParticleContainer::ReadParameters ()
         {Hipace::m_depos_order_xy % 2, Hipace::m_depos_order_xy % 2};
     queryWithParserAlt(pp, "reorder_idx_type", idx_array, pp_alt);
     m_reorder_idx_type = amrex::IntVect(idx_array[0], idx_array[1], 0);
-    queryWithParserAlt(pp, "insitu_period", m_insitu_period, pp_alt);
+    queryWithParserAlt(pp, "insitu_period", m_insitu_period.m_func_str, pp_alt);
+    m_insitu_period.compile();
     m_insitu_file_prefix = Hipace::m_output_folder + "/insitu";
     const bool set_file_prefix =
         queryWithParserAlt(pp, "insitu_file_prefix", m_insitu_file_prefix, pp_alt);
@@ -281,7 +282,7 @@ PlasmaParticleContainer::InitData (const amrex::Vector<amrex::Geometry>& geom3d)
 
     InitParticles(m_u_std, m_u_mean, m_radius, m_hollow_core_radius);
 
-    if (m_insitu_period > 0) {
+    if (m_insitu_period.isNonZero()) {
 #ifdef HIPACE_USE_OPENPMD
         AMREX_ALWAYS_ASSERT_WITH_MESSAGE(m_insitu_file_prefix !=
             Hipace::GetInstance().m_openpmd_writer.m_file_prefix,
diff --git a/src/utils/IOUtil.H b/src/utils/IOUtil.H
index b3fa89838d..0f662bdea4 100644
--- a/src/utils/IOUtil.H
+++ b/src/utils/IOUtil.H
@@ -12,6 +12,7 @@
 #include <AMReX_IntVect.H>
 #include <AMReX_RealVect.H>
 #include <AMReX_MultiFab.H>
+#include <AMReX_Parser.H>
 
 #include <cstdint>
 #include <iostream>
@@ -46,16 +47,27 @@ namespace utils
     std::vector<double>
     getReversedVec ( const amrex::Real* v );
 
-    /** \brief
-     * returns whether output should be writen to file
-     * \param[in] output_period period of the output
-     * \param[in] output_step current step
-     * \param[in] max_step maximum step of simulation
-     * \param[in] output_time physical time of the current step
-     * \param[in] max_time maximum simulation time
-     */
-     bool doDiagnostics (int output_period, int output_step, int max_step,
-                    amrex::Real output_time, amrex::Real max_time);
+    struct DiagPeriod {
+        std::string m_func_str;
+        amrex::Parser m_parser;
+        amrex::ParserExecutor<2> m_exe;
+
+        DiagPeriod (const char * str) : m_func_str{str} {}
+
+        void compile ();
+
+        bool isNonZero () const { return m_func_str != "0"; }
+
+        /** \brief
+         * returns whether output should be writen to file
+         * \param[in] output_step current step
+         * \param[in] max_step maximum step of simulation
+         * \param[in] output_time physical time of the current step
+         * \param[in] max_time maximum simulation time
+         */
+        bool doDiagnostics (int output_step, int max_step,
+                            amrex::Real output_time, amrex::Real max_time) const;
+    };
 
     struct format_time {
         double seconds = 0;
diff --git a/src/utils/IOUtil.cpp b/src/utils/IOUtil.cpp
index fd8c5607d7..b4014b75ea 100644
--- a/src/utils/IOUtil.cpp
+++ b/src/utils/IOUtil.cpp
@@ -6,6 +6,7 @@
  * License: BSD-3-Clause-LBNL
  */
 #include "IOUtil.H"
+#include "Parser.H"
 
 #include <AMReX_IndexType.H>
 #include <AMReX_IOFormat.H>
@@ -71,10 +72,16 @@ utils::getReversedVec ( const amrex::Real* v )
   return u;
 }
 
+void
+utils::DiagPeriod::compile () {
+    m_exe = makeFunctionWithParser<2>(m_func_str, m_parser, {"current_step", "current_time"});
+}
+
 bool
-utils::doDiagnostics (int output_period, int output_step, int max_step,
-               amrex::Real output_time, amrex::Real max_time)
+utils::DiagPeriod::doDiagnostics (int output_step, int max_step,
+                                  amrex::Real output_time, amrex::Real max_time) const
 {
+    const auto output_period = static_cast<amrex::Long>(m_exe(output_step, output_time));
     return output_period > 0 && (
         (output_time == max_time) ||
         (output_step == max_step) ||