Problem mit eigener F4-Hilfe

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AT SELECTION-SCREEN ON VALUE-REQUEST FOR...

Code: Alles auswählen.

SELECT-OPTIONS:
      s_matnr FOR mvke-matnr MATCHCODE OBJECT sd_mat1,    
      s_normt FOR mara-normt.

....

AT SELECTION-SCREEN ON VALUE-REQUEST FOR s_normt-low. 
  PERFORM f4_help_normt. 
  LEAVE TO SCREEN 1000. 

....

FORM f4_help_normt.

  DATA: lt_fields LIKE TABLE OF dynpread,
        l_fields LIKE LINE OF lt_fields.

  IF it_normt[] IS INITIAL.
    PERFORM get_value_normt.
  ENDIF.
* Werteliste anzeigen und Auswahl zurückliefern
  CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
       EXPORTING
            retfield        = 'MATNR'
            window_title    = ' '
            value_org       = 'S'
            multiple_choice = 'X'
            display         = 'F'
       TABLES
            value_tab       = it_normt
            return_tab      = it_return_tab
       EXCEPTIONS
            parameter_error = 1
            no_values_found = 2
            OTHERS          = 3.
* Werte an Parameter übergeben
  IF sy-subrc = 0 AND NOT it_return_tab IS INITIAL.
    LOOP AT it_return_tab.
      s_matnr-sign = 'I'.
      s_matnr-option = 'EQ'.
      s_matnr-low = it_return_tab-fieldval.
      APPEND s_matnr.
      CLEAR s_matnr.
    ENDLOOP.
  ENDIF.

  LOOP AT s_matnr.
    l_fields-fieldname = 'S_MATNR-LOW'.
    l_fields-fieldvalue = s_matnr-low.
    APPEND l_fields TO lt_fields.
  ENDLOOP.

  CALL FUNCTION 'DYNP_VALUES_UPDATE'
       EXPORTING
            dyname               = 'ZSDMT_MATERIALINFO_VERTRIEB'
            dynumb               = '1000'
       TABLES
            dynpfields           = lt_fields
       EXCEPTIONS
            invalid_abapworkarea = 1
            invalid_dynprofield  = 2
            invalid_dynproname   = 3
            invalid_dynpronummer = 4
            invalid_request      = 5
            no_fielddescription  = 6
            undefind_error       = 7
            OTHERS               = 8.


  CLEAR   it_return_tab.
  REFRESH it_return_tab.

ENDFORM.

....

FORM get_value_normt.

  DATA: lt_fields LIKE TABLE OF dynpread,
        l_fields LIKE LINE OF lt_fields.

  l_fields-fieldname = 'S_NORMT-LOW'.
  APPEND l_fields TO lt_fields.
  l_fields-fieldname = 'S_NORMT-HIGH'.
  APPEND l_fields TO lt_fields.

  CALL FUNCTION 'DYNP_VALUES_READ'
       EXPORTING
            dyname     = 'ZSDMT_MATERIALINFO_VERTRIEB'
            dynumb     = '1000'
       TABLES
            dynpfields = lt_fields.

  READ TABLE lt_fields INDEX 1 INTO l_fields.
  IF NOT l_fields-fieldvalue IS INITIAL.
    s_normt-sign = 'I'.
    s_normt-option = 'EQ'.
    s_normt-low = l_fields-fieldvalue.
    APPEND s_normt.
  ENDIF.
  READ TABLE lt_fields INDEX 2 INTO l_fields.
  IF NOT l_fields-fieldvalue IS INITIAL.
    s_normt-sign = 'I'.
    s_normt-option = 'EQ'.
    s_normt-low = l_fields-fieldvalue.
    APPEND s_normt.
  ENDIF.

  SELECT matnr normt FROM mara
    INTO CORRESPONDING FIELDS OF TABLE it_normt
         WHERE normt IN s_normt.

ENDFORM.                    " get_value_normt