ALV Summation

HI, I have defined my field catalogue like

wa_fieldcat-fieldname = 'TOTQTY'.

wa_fieldcat-seltext_l = 'Total Qty'(006).

wa_fieldcat-qtabname = 'GT_LIST'.

wa_fieldcat-qfieldname = 'MEINS'.

wa_fieldcat-do_sum = 'X'.

APPEND wa_fieldcat TO gt_fieldcat.

I'm not getting sum value at the end of the list, Any thing missing. I appreciate your help.

Thanks.