validation of file path

OPEN DATASET g_filepath IN TEXT MODE FOR INPUT

MESSAGE g_msg.

IF sy-subrc = 0.

MESSAGE e001 WITH 'File Already Exist' g_msg .

CLOSE DATASET g_filepath.

leave Program.

ELSE .

CLOSE DATASET g_filepath.

ENDIF.

here when control goes to ELSE. then may be file doesnot exist or Invalid File Path.

if File doesnot exist then OK .

what to do when Invalid File Path .

Plz reply