(form "77010" (size 52  7)
   (heading "Marker Position")
   (field "position" (position 30 3) (display_length  16) (input allowed)
    (value_in "Evenly spaced" "Weighted spacing")
    (null disallowed) (max_length 16)
    (help "77010_TIP"))
  (default_buttons)
)