(form "20060" (size 53 10)
  (heading "SELECT BLOCK MODEL SOURCE")
  (label (position  2  3) (text "Model"))
  (label (position  2  4) (text "Attribute"))
  (label (position  2  6) (text "Constrain data"))
  (field "model" (position 11  3) (display_length 40) (input allowed)
    (translate lower) (null disallowed) (max_length 40)
    (file input (extension trim "*.mdl"))
  )
  (field "attribute" (position 11  4) (display_length 10) (input allowed)
    (translate lower) (null disallowed) (max_length 30))
  (field "constrain" (position 19  6) (display_length  1) (input allowed)
    (value_in "Y" "N")
    (translate upper) (null allowed) (max_length 1))
  (default_buttons)
)