Don't ask me how to do this, but have you considered having a successful login create an object with a property value you can check prior to opening a linked web page? If the individual browsing the web does not log in, then they would not have an instance of the "LoginSuccessfullyAuthenticated" object to check prior to loading a web page. You could store this object in memory and know that upon reboot it would be destroyed. Alternately you could build in a "time bomb" of sorts into the instance of the object that would destroy the "LoginSuccessfullyAuthenticated" object after a predetermined time interval.
Another method (less sophisticated) would be to create a cookie upon a successful login. This cookie could then be checked prior to loading specific web pages stored upon your site.
Hope this helps.