Pedie
Am I missing something?
You want to make it so that you yourself can't open forms in desgin mode?
Do you actually want to stop other people viewing the form in design mode?
Before deploying the front end to user should compile the front end into a MDE/ADE/ACCDE. This disable the ability to modify forms, reports, and modules.
To make design changes you use the "master/source code" database (.mdb/.accdb/.adp) to make changes. The compile a new front end for deployment. You never let the yser have access to your "master/source code" database.
Pedie
If you are using Access 2010 (or 2007?) just goto the File tab, then Save & Publish and choose Make ACCDE.