You can change all access to the backend tables to go through queries, (ex: all forms populated and updated through queries rather than directly into the tables).
Then go into the properties of each query and set the "Run Permissions" to owner's. Go into Tools menu, select Security go into user and group acounts and permissions, restrict their access to the tables and grant them the rights they need to the queries.
Unless this is a small app, all of this is a lot of work and should be done right from the beginning of construction, but it could still be done if you have some coding experience.
Hope this helps.