Hi!
If security is that critical, and your users are that advanced in Access, then your only option is to totally lock down the Db. What Databaseguy gave you in his post is a good start but, with users like yours, you will need to go farther. In Tools/Startup you will need to unclick showing the database window(if for some reason you must let them use the database window, hide all of the objects they will not be allowed to use) basically uncheck every box, including the ones you find after hitting the advanced button. You will also need to make your own toolbar and menubar and set them as the defaults in the startup window and(I think) for your forms. All of this together will lock the Db tight enough that(after you disable the bypass key) you will not be able to get into it either, so, on your way out, you might as well make an .mde file out of the Db. Of course, you will need to make a copy for your own use so you have full access and can make changes if necessary, and they are always necessary. There are some good threads and FAQs which cover these topics as well.
hth
Jeff Bridgham