F4 help for a selection screen parameter with filename created dynamically

Question

Hi All,
          I have a requirement where in an F4 help should be present for a selection screen parameter. After selecting the filepath and clicking OK button on the Dialog, the filename should be dynamically get created in the selection screen parameter field. For example:
if the path is D:\DOCS then at the end of DOCS the filename should automatically get populated.
Like below string:
D:\DOCS\new.txt
Is there any function module or method which does this kind of activity.
Thanks in advance,
Deepak

Answer 1

this code will help:
FORM get_filename  CHANGING p_filename.
  DATA      : lv_filename  TYPE string,
              lv_rc TYPE i,
              li_filetable TYPE filetable.
  CONSTANTS : lc_fname TYPE string VALUE 'ZRPP4000.XLS',
              lc_fpath TYPE string VALUE 'C:\',
              lc_extn TYPE string VALUE 'XLS'.
  CALL METHOD cl_gui_frontend_services=>file_open_dialog
    EXPORTING
      default_filename        = lc_fname
      initial_directory       = lc_fpath
      default_extension       = lc_extn
    CHANGING
      file_table              = li_filetable
      rc                      = lv_rc
    EXCEPTIONS
      file_open_dialog_failed = 1
      cntl_error              = 2
      error_no_gui            = 3
      not_supported_by_gui    = 4
      OTHERS                  = 5.
IF  sy-subrc = 0 .
    READ TABLE li_filetable INTO lv_filename INDEX 1.
    IF sy-subrc = 0.
      p_filename = lv_filename.
    ENDIF.
  ENDIF.
  REFRESH li_filetable.
  CLEAR:lv_filename.
ENDFORM.                    "get_filename
" p_filename is selection screen parameter