Use Access Developer Edition to destribute your MDB with the Access Run-Time. This Run-Time don¦t have the feature to open the database window. BUT BE CAREFULL if the User PC have your Access Version the Run-Time is not installed, so the MDB use the Access default features.
In Developer Edition Go: *TOOLS* - *xxxDB PROPRETIES*, and protect your VBA with a Password. This Password is required only when you enter the Database, and is typed one time per Session.
Distribute the Database as a MDE File. All FORMS, REPORTS MODULES and CLASS MODULES will not be avaible in Design View. All VBA is compiled and the Database become smaller.