Hi Shilpa,
Find any enhancements points are possible before append statement. But in most of the case in standard, we won't get like this.
Before calling REUSE_ALV_GRID_DISPLAY, we need to fill the values for the newly added columns. The Function REUSE_ALV_GRID_DISPLAY/REUSE_ALV_LIST_DISPLAY is written in some subroutine, at the beginning you may find some enhancement points in there, we can modify the values of final internal table using field symbol concept.
LOOP AT OBJECT_TAB ASSIGING <FS_OBJECT>.
<FS_OBJECT>-FIELD1 = 'NEW_VALUE'.
ENDLOOP.
Regards
Rajkumar Narasimman