It might be needed to identify the first iteration of a timestep in a UDF, for example when using a DEFINE_ADJUST macro which is called every iteration by default, even for transient analyses. The UDF below is an example that uses a if clause to check if the first iteration is currently being executed. The variable first_iteration is built in and no special declaration is needed. Also, if you want to run in reverse at the end of a time step, you can also use the DEFINE_EXECUTE_AT_END macro. DEFINE_ADJUST(myadjust,d) { if (first_iteration){ Message(“FIRST ITERATION!!n”); } }