I need assistance in determining the best way to implement something.  On a site, I have a business requirement on only two to display a pop-up survey window (I know).  However, I only want to display this survey under two conditions. 

1. If the visitor is not only leaving the current page, but also the site.
2. If the visitor has never taken the survey before.

Detecting whether the survey has been take is easy.  We plan on assigning a cookie upon completion to check for later.  However, I am at a loss as to how we can consistently and accurately determine item one. 

I have toyed around with the JavaScript window.location.href object during the client-side onUnload event, but it does not appear to tell me what the next URL is, only the current one.

I have a licence for and have installed the PageBlaster Module on this site, so injecting the necessary code for just these two pages (tabs) can be done using that module.  But how do I detect if the visitor is leaving the site?