Variables to lock/unlock course navigation

Hello! The main menu will instruct the user to select from either the open (unlocked) version of the course or the restricted/locked version. How can I set this up? Can I default the menu to locked and use a variable to unlock the whole course if the user selects the unlocked version? Is that possible? Or do I need to default the whole course menu to unlocked and then create many many variables within the course to lock it up? Thanks!