Quick answer:Yes. Details: There are some project settings that can be changed by the script during simulation, such as wavelength. The script can change a user defined parameter. If the simulation parameter is defined by a user defined parameter, then the value used will be changed when the script changes the user parameter. Wavelength can be defined and changed during simulation this way. Unfortunately not all simulation parameters can be defined with a user parameter. Propagation step is one of those. On the other hand, the propagation step can be varied over the simulation by using the Calculation Zone in the OptiBPM Designer. The Calculation Zone also permits definition of propagtion step by user defined variable. Therefore the script can change propagation step within any Calculation Zone.