为选择屏幕的字段设置F4帮助

PARAMETERS: p_bukrs(4) TYPE C MATCHCODE OBJECT H_T001.
AT SELECTION-SCREEN  ON VALUE-REQUEST  FOR  p_bukrs.
        PERFORM frm_f4 CHANGING p_bukrs.
FORM frm_f4 CHANGING p_value.
   CONSTANTS cns_retfield TYPE fieldname VALUE ‘BUKRS‘.   
   DATA: BEGIN OF lt_value OCCURS 0, 
            bukrs LIKE t001-bukrs, "公司代码     
            butxt LIKE t001-butxt, " 公司名称      
            END OF lt_value. 
   DATA: lt_retuen LIKE TABLE OF  ddshretval WITH HEADER LINE.  
  SELECT bukrs butxt FROM t001 INTO TABLE lt_value.    
CALL FUNCTION ‘F4IF_INT_TABLE_VALUE_REQUEST‘ 
    EXPORTING 
        retfield        = cns_retfield  
        value_org       = ‘S‘   
   TABLES 
       value_tab       = lt_value     
      return_tab      = lt_retuen   
   EXCEPTIONS 
       parameter_error = 1     
   no_values_found = 2      
  OTHERS          = 3.  
  IF sy-subrc = 0. 
    READ TABLE lt_retuen  INDEX 1.    
    p_value  = lt_retuen-fieldval. 
  ELSE. 
  ENDIF. 
ENDFORM.                    "frm_f4_bukrs