Calling custom function module in background task

Hi All,

I need to call a custom function module in my program and run it as a background task. I used

      CALL FUNCTION 'Z_SD_SERV_ORDER_CREATE' IN BACKGROUND TASK

        TABLES

          T_FLTHDR       = LT_FLTHDR

               .

IF SY-BATCH EQ 0.

ENDIF.

But the SY - BATCH returns me SPACE . I checked in SM37 also. There was no background job running. Can anyone please help me out on this?

Regards,

Siju