Hi Mr. Thomas refer this code.
IF gs_sub_fcat-fieldname = 'PRCTR'.
REFRESH : gt_sort.
wa_sort-fieldname = 'PRCTR'.
wa_sort-up = 'X'.
wa_sort-subtot = 'X'.
wa_sort-tabname = 'gt_ordsub1'.
wa_sort-expa = 'X'.---------------------------------> This is importand for Expand
APPEND wa_sort TO gt_sort.
CLEAR : wa_sort.
then pass the gt_sort to FM 
Regards
TK.Srithar