(form "00411" (size 45  5)
  (help "00411_TIP_0")
  (heading "SELECT A WORKING GRID")
  (label (position  2  3) (text "Grid name"))
  (field "grdname" (position 16  3) (display_length 26) (input allowed)
    (null allowed) (max_length 26)
    (file (extension trim "*.grd")))
  (default_buttons)
)