User Command not working with 'REUSE_ALV_HIERSEQ_LIST_DISPLAY'

Hello ABAP gurus,

I am using 'REUSE_ALV_HIERSEQ_LIST_DISPLAY' for ALV

for hierarchical lists. The call looks like this

CALL FUNCTION 'REUSE_ALV_HIERSEQ_LIST_DISPLAY'

EXPORTING

I_CALLBACK_PROGRAM = GV_REPID

I_CALLBACK_USER_COMMAND = SLIS_EV_USER_COMMAND

I_CALLBACK_PF_STATUS_SET = SLIS_EV_PF_STATUS_SET

IT_FIELDCAT = GT_SLIS_FCAT

I_SAVE = GC_SAVE

IT_EVENTS = GT_EVENTS

IS_LAYOUT = GS_LAYOUT

I_TABNAME_HEADER = GC_TABNAME_HEADER1

I_TABNAME_ITEM = GC_TABNAME_DETAIL1

I_STRUCTURE_NAME_HEADER = GC_STRUCTURE_HEADER

I_STRUCTURE_NAME_ITEM = GC_STRUCTURE_DETAIL

IS_KEYINFO = GS_KEYINFO

TABLES

T_OUTTAB_HEADER = GT_OUTPUT_HEADER1

T_OUTTAB_ITEM = GT_OUTPUT_DETAIL1

EXCEPTIONS

PROGRAM_ERROR = 1

OTHERS = 2.

I have populated SLIS_EV_USER_COMMAND with the form name on user command and GT_EVENTS with the value 'USER_COMMAND' . Still on clicking any row in the ALV list am getting the message 'Choose a valid function'. Can anybody let me know if I am missing something?. Any pointers would be highly appreciated.

TIA

sharath