How to create an F4 for a file

Data: l_file LIKE rlgrap-filename.

CALL FUNCTION 'F4_FILENAME'
EXPORTING
program_name = syst-cprog
dynpro_number = syst-dynnr
field_name = 'L_FILE'
IMPORTING
file_name = l_file.

another similar way:

DATA: return_code TYPE i,
files LIKE file_table OCCURS 0.

CALL METHOD cl_gui_frontend_services=>file_open_dialog
EXPORTING
WINDOW_TITLE = 'Title'
* DEFAULT_EXTENSION =
* DEFAULT_FILENAME =
* FILE_FILTER =
* WITH_ENCODING =
* INITIAL_DIRECTORY =
* MULTISELECTION =
CHANGING
file_table = files
rc = return_code
* USER_ACTION =
* FILE_ENCODING =
* EXCEPTIONS
* FILE_OPEN_DIALOG_FAILED = 1
* CNTL_ERROR = 2
* ERROR_NO_GUI = 3
* NOT_SUPPORTED_BY_GUI = 4
* others = 5
.
IF sy-subrc <> 0.
* MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
* WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
ENDIF.