filtering user id based on condition

I have one requirement in NWBC Tcode at the time of creating request we have to filtering user id (SAPTECH ID) based on some filtering condition. And those id which will fulfill the filtering criteria will be shown in the below screen shot .After debugging I have found class CL_GRAC_USER_REP and method SEARCH_USER where I can do the enhancement .But at the time doing implicit enhancement when we put break-point inside ENHANCEMENT and END ENHANCEMENT the control is not going to that position. So my question is that is there any other way to do it.Any expert suggestion.

Regads,

Abhishek Bhowmik