Assuming your have control over your PHP scripts, you could swap out the current navbar for a second hidden one.
I might display the NavBars as standalone pages and present them in a IFRAME where the source is controlled by a registered flag.
It then begs the question as to whether the extra pages and the special NavBar are also equally protected?
I am sure that what you are trying to achieve cannot be done without a solid technical specification underpinning it all.
Acorn
Bookmarks