Number range enhancement in invoice list VF21

Dear gurus

As I know, if another number range need to be determined in billing document creation instead of the one in vofa assigned, user-exit RV60AFZZ  FUNCTION'userexit_number_range'is the place where we write. However now the senerio is invoice list, I try to put break-point in the same place, but program never goes into debug mode. Does anyone could give me some information where should I enhance in order to have different number range for same invoice list type?

thanks！

BR

Peng Tang