How to trigger userexit Plant_selection (Include RV03VFZZ)

Dear All,

I need your help because i'm trying to analyze how to perform an ATP multiplant without APO.

From other posts I've realized that a possible solution is to write ABAP logic within user exit USEREXIT_PLANT_SELECTION in the Include RV03VFZZ.

I don't know how to trigger this userexit. I've tried to put a breakpoint. I've seen inside code that the  form is called from routine WERKE_ERMITTELN in LV03VF0W but which are the possible events that make the system call this routine?

Any suggestion will be really appreciated.

Many thanks

Angelo Gaiatto