Output problem in SAPScript

Dear gurus

I have created a SAPScript form  for PO.

I have created two windows as

HEADER

MAIN

Output of main is coming correct but HEADER window output is not coming correct .

In HEADER window , only last record which i used to fill in selection screen is coming.

in this window, only PO number 52 is displayed ,but i have entered range from 50 to 52.

Here's the code for the WRITE FM.

form write_form.

   CALL FUNCTION 'WRITE_FORM'
     EXPORTING
       ELEMENT  = 'HEADER'
*     FUNCTION = 'SET'
*     TYPE     = 'BODY'
       WINDOW   = 'HEADER'.
   IF SY-SUBRC <> 0.

   ENDIF.



   CALL FUNCTION 'WRITE_FORM'
     EXPORTING
       ELEMENT  = 'ITEM HEADER '
*     FUNCTION = 'SET'
*     TYPE     = 'BODY'
       WINDOW   = 'MAIN'.
   IF SY-SUBRC <> 0.

   ENDIF.


   loop at it_final into wa_final.
     CALL FUNCTION 'WRITE_FORM'
       EXPORTING
         ELEMENT  = 'ITEM LINE '
*       FUNCTION = 'SET'
*       TYPE     = 'BODY'
         WINDOW   = 'MAIN'.
     IF SY-SUBRC <> 0.

     ENDIF.
   endloop.

endform.                    "write_form

In this loop to MAIN window is working fine . But loop to HEADER window is not working correct.

Can anyone help me why this is happening to output of HEADER window.

Help?

Thanks

Regards

karan