Thank you, Dom. You'd be surprised how a shot in the wallet catches someone's attention when physical threats of violence won't. And while a really determined user can bypass a lot of stuff, you can at least take the approach of making it a challenge. With this warning embedded in your code.
Go ahead and use the switchboard. Have it set up something in the Forms_Open routine such that you have a context variable in a public module. Have every form and every report look at the context variable. The moment someone breaks in to your DB bypassing the switchboard, you have a case where that context variable isn't there any more. Use that to trap the unsuspecting k-user.
Now, if this is REALLY a valuable DB, talk to your network admin. Have that person place audit events on all who Open the database file. WINDOWS audit events. Then have your switchboard update a file outside of the database.
The trail will be that you will have Windows Open-file events that do NOT correspond to the external log file created outside the database.
Take THAT evidence to the boss and make it clear that k-user is costing the company time and money - and risking data loss.
After that, you will find out whether your DB or the k-user is more valuable. And if that leads to a career choice, so be it.
And if all else fails, I've got a Cajun cousin, Ol' Boudreaux, who keeps a lot of 'gators in his back yard. (Well...., his back swamp.) Boudreaux can make ANYONE disappear.