well you could always check if the links has been pressed (on serverside, by 'link-redirects') ... but ... there's still ways to override such stuff, and you'd need to have a good session handler aswell, and the effort needed to create it I doubt will be worth it ...
so nothing you can 'force' and be able to trust will do the right things ... you just have to trust the users ... and considering where these type of things are used quite frequently ... I woulnd't give much for trusting the users to do anything
so ... I'd say, keep your fingers crossed that at least someone clicks them (I suppose you could always google after a finished script, if you're lucky someone have distrobuted their work, but be sure to check the code)