Why dont you use the below mentioned syntax. This will return you back the results of the processing in table LT_RETURN
Call function FM1 starting new task
PERFORMING get_return ON END OF TASK
Wait untile GV_FLAG is X. " GV_FLAG is global
Create subroutine
FORM get_return USING TASKNAME.
RECEIVE RESULTS FROM FUNCTION FM1
tables
return = lt_return
gv_flag = 'X'.
ENDFORM.