Hi Dave--
You might be able to use a "paste" document callback to check the paste
buffer for entity references, and check each one to see if it is defined
for the target document; if not, you can abort the paste with a warning
message. See the help center topic for "doc_add_callback" for details on
how to set up this kind of callback.
--Clay
Clay Helberg
Senior Consultant
TerraXML