F4 Help on selection screen

Question

Hello all,
    In my selection screen based up on one selection field value i.e. matnr i need to display all the serilanumbers.
I have written using AT SELECTION SCREEN ON VALUE REQUEST.
and am to display , but my problem is after entering the material value , I need to ENTER and pressing on F4 only it is giving.
My req is: As soon as Enter the matnr value , and i will press F4 on the serilnumber field.
But the value of material is not coming directly to the At selection screen on value request.
Please tell me since urgent tome

Answer 1

first read the values form Screen..
  REFRESH iv_vbeln.
  DATA: itab_dynpfields_9000 LIKE dynpread OCCURS 0 WITH HEADER LINE,
       t_dynpfields_9000    LIKE dynpread.
  DATA: return_values_9000   LIKE ddshretval OCCURS 0 WITH HEADER LINE.
  REFRESH itab_dynpfields_9000. CLEAR: t_dynpfields_9000.
  t_dynpfields_9000-fieldname = 'S_LFDAT-LOW'.
  APPEND t_dynpfields_9000 TO itab_dynpfields_9000.
  t_dynpfields_9000-fieldname = 'P_WERKS'.
  APPEND t_dynpfields_9000 TO itab_dynpfields_9000.
*break abap_dev.
  CALL FUNCTION 'DYNP_VALUES_READ'
    EXPORTING
      dyname               = sy-repid
      dynumb               = sy-dynnr
    TABLES
      dynpfields           = itab_dynpfields_9000
    EXCEPTIONS
      invalid_abapworkarea = 1
      invalid_dynprofield  = 2
      invalid_dynproname   = 3
      invalid_dynpronummer = 4
      invalid_request      = 5
      no_fielddescription  = 6
      invalid_parameter    = 7
      undefind_error       = 8
      double_conversion    = 9
      stepl_not_found      = 10
      OTHERS               = 11.
  IF sy-subrc <> 0.
   MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
   WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.
  LOOP AT itab_dynpfields_9000.
    CASE itab_dynpfields_9000-fieldname.
      WHEN 'S_LFDAT-LOW'.
        lv_dat =  itab_dynpfields_9000-fieldvalue.
      WHEN 'P_WERKS'.
        lv_werks = itab_dynpfields_9000-fieldvalue.
    ENDCASE.
  ENDLOOP.
Regards,
Vamshidhar .