VMS Help UIL, Compile Time Errors, UNSUPPORTED  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  WARNING:   Each  widget  or  gadget  supports  a  specific  set   of
  arguments,  reasons, and children.  The particular argument, reason,
  or child you specified is not supported for this widget or gadget.

  USER ACTION:  See the UIL built-in tables  in  the  "VMS  DECwindows
  User   Interface  Language  Reference  Manual"  for  the  arguments,
  reasons, and children supported for each  object.   If  a  low-level
  creation routine accepts an argument that UIL rejects, this does not
  necessarily indicate that  the  compiler  is  in  error.   Low-level
  routines   ignore  arguments  that  they  do  not  support,  without
  notifying you that the argument is being ignored.