To prevent problems like this, the application should be split into a
front-end (containing the queries, forms, reports, macros and modules),
linked to a back-end (containing the tables and relationships). When you're
making changes, you make them to the front-end only. When you're done, you
give them a new copy of the front-end, and make sure that it's pointing to
the correct back-end. Note that each user should have his/her own copy of
the front-end, preferably on his/her hard drive, with only the back-end
existing on the server.

You can split their existing database now, and only give them the new
front-end.

References you might find useful for this topic include:

http://www.mvps.org/access/tables/tbl0009.htm
http://www.granite.ab.ca/access/splitapp/index.htm
http://www.granite.ab.ca/access/autofe.htm