This is my code.
CALL FUNCTION 'BAPI_DELIVERYPROCESSING_EXEC' STARTING NEW TASK task PERFORMING return_form ON END OF TASK
TABLES
request = tbl_request .
* createditems = createditems
* return = return.
WAIT UNTIL gr_flag = 'X'.
createditems[] = gt_createditems[].
return[] = gt_return[].
FORM return_form USING task.
RECEIVE RESULTS FROM FUNCTION 'BAPI_DELIVERYPROCESSING_EXEC'
TABLES
createditems = gt_createditems
return = gt_return.
gr_flag = 'X'.
ENDFORM.