Dynamic F4 Help based on the Value of other Field

Follow the below steps  to provide the dynamic F4 help for a field on the selection screen based on the value of other field.

• Read the value of the first field on the selection screen using function module DYNP_VALUES_READ.
• Build an internal table for the dynamic help of second field on the selection screen based on the value read from above step.
• Display the F4 help using function module F4IF_INT_TABLE_VALUE_REQUEST

TYPES: BEGIN OF ty_matnr,
       werks TYPE marc-werks,
       matnr TYPE makt-matnr,
       maktx TYPE makt-maktx,
       END OF ty_matnr.
*--------------------------------------------------------------*
*Data Declaration
*--------------------------------------------------------------*
DATA: gwa_matnr      TYPE ty_matnr,
      gt_matnr       TYPE TABLE OF ty_matnr.
DATA: gt_return      TYPE TABLE OF ddshretval,
      gwa_return     TYPE ddshretval.
DATA: gwa_dynpfields TYPE dynpread,
      gt_dynpfields  TYPE TABLE OF dynpread.
DATA: gv_werks       TYPE marc-werks.
*--------------------------------------------------------------*
*Selection-Screen
*--------------------------------------------------------------*
PARAMETERS: p_werks TYPE marc-werks OBLIGATORY.
PARAMETERS: p_matnr TYPE mara-matnr.

*--------------------------------------------------------------*
*Selection-Screen on Value-Request
*--------------------------------------------------------------*
AT SELECTION-SCREEN ON VALUE-REQUEST FOR p_matnr.

  REFRESH gt_dynpfields.

  gwa_dynpfields-fieldname = 'P_WERKS'.
  APPEND gwa_dynpfields TO gt_dynpfields.

*Get plant value on the selection screen
  CALL FUNCTION 'DYNP_VALUES_READ'
    EXPORTING
      dyname               = sy-repid
      dynumb               = sy-dynnr
    TABLES
      dynpfields           = gt_dynpfields
    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.

  READ TABLE gt_dynpfields INTO gwa_dynpfields
         WITH KEY fieldname = 'P_WERKS'.
  IF sy-subrc = 0.
    gv_werks = gwa_dynpfields-fieldvalue.
  ENDIF.

*Get values from the database based on plant
  SELECT a~werks
         a~matnr
         b~maktx
         UP TO 10 ROWS
         INTO TABLE gt_matnr
         FROM marc AS a
         INNER JOIN makt AS b
         ON a~matnr = b~matnr
         WHERE a~werks = gv_werks
           AND b~spras = 'EN'.

  CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
    EXPORTING
      retfield        = 'MATNR'
      value_org       = 'S'
    TABLES
      value_tab       = gt_matnr
      return_tab      = gt_return
    EXCEPTIONS
      parameter_error = 1
      no_values_found = 2
      OTHERS          = 3.

  READ TABLE gt_return INTO gwa_return INDEX 1.
  IF sy-subrc = 0.
    p_matnr = gwa_return-fieldval.
  ENDIF.

Selection Screen Output

Enter a value for Plant and press F4 help on Material.