change of Search help for location field in report incident

Hi All,

         i have added new fields Region,BSA in the report incident form .here based on the region entered in the search help the corresponding bsa have to be displayed in the search help of BSA .these are achieved customising  the search help exit FM    EHFND_SHLP_EXIT_F4_BOBF_QUERY.

similarly based on the BSA entered in the BSA field Location field search help should filter the values and display .the isues here are

1. the location field and search help attached are standard and they are being used in many instances .

2.when i click on the f4 help the control doesnt stop any where in the feeder class CL_EHHSS_INC_Q_LOC_UI_FRM of the form  though i put the breakpoints .ie the event on enter locid is not getting triggered.

my question is where can i write the code to filter the values being displayed in the location search help.

Thanks&Regards

Luxmi