Placing a session limit on scripts

Can this be done? What I'd like to do is set a limit of once-per-script on my site for bigger/heavier pages. For example, I love MPDev's VBISpy, and I often see users with several tabs open to the page. I'd like them to only have ONE instance of the page/script, and any additional connections from that user would simply throw a "you are allowed only one instance of (script)" error.

[Opserty]

I'd be careful, you'd probably annoy the heck out of your users. People use browser tabs for a reason, it make their browsing quicker, easier and more productive. Furthermore once a page has been sent to the end browser it doesn't use any more server resources so basically having many tabs open is just like clicking a lot of links.

Is there even a reliable way to detect this? What if some accidentally closes the window and then wants to get back on?

Maybe instead you should look at optimising the scripts themselves instead of trying to limit access.

Just my 2 cents

I'd want to use it situationally. There's no reason for someone to have multiple tabs of an AJAX post roller open.