and even if I removed the duplicate record menu pull down, they know the keyboard command.
Removing the menu option with a custom menu also disables the keyboard short cut.
One option may be to update permissions so that they do not have permission to create or duplicate a new record. Then you can put buttons on the layout that performs scripts with the "run will full access privileges" setting selected and they will be able to create or duplicate a record only by clicking a button that you provide for that purpose.
(And Set field can be used to clear a field. Then you do not have to have the field present and accessible on your layout in order to clear it.)
Great info, Phil, as always.