The .LDB file is just a database file, too. You should be able to open it and look at the tables. (They are hidden, so you might have to muck your options a bit to see hidden objects.)
The usual way to control users is a startup form that either is part of your switchboard (if that's what you have) or looks like a company logo. If the latter, don't close the logo. Instead, minimize it and hide it.
In the form's OnLoad routine, check some obscure table that might be hidden or even external to the main .MDB to see if you have updated some obscurely-named table to have a record with an obscurely spelled keyword that says "Send Everyone Away." Make the code also check that it doesn't kill itself if you use a hidden table in the same MDB file. But if it is external, that isn't needed. Anyway, once this code is set, make every person trying to log in just go away. DoCmd.Quit works here.
Then in the same OnLoad routine, set up the form's Timer. In the OnTimer routine, query that same table for the same condition once per minute or so. Again, DoCmd.Quit works fine to kill the app.
Now, when you need to force everyone out of the DB, go into the OTHER database file, add this obscure record to the obscure table, and exit. This OTHER MDB doesn't have the startup form so you can update the obscure table without having to log in to the closely protected MDB file.
If you did this right then, within no more than a couple of minutes, everyone should be out. Now if you have an .LDB file, it is a leftover. Kill the file, remove the obscure record value, and do your edit, update, or whatever.
Perhaps as a wrinkle to this, you can have two codes. One that kills everyone and one that won't kill members of the Admins group. That way you can do the update in isolation and can update a hidden table in the same MDB as the you had to update. This is a style choice.
