Hmmm, I'd be very surprised if you could easily pull that one off. At least by staying in the cozy confines of RoboHelp.
However, I do know that it's possible to cause an HTML page to redirect. And although I've not researched it, I do believe it can be redirected to open an email. And assuming that you are talking about a system that resides on the web, I'm pretty sure that the web server keeps count on how many times a page has been visited. So it might be possible to achieve by replacing the email variable with an HTML page that redirects.
If I'm totally off my nut here, hopefully someone will come along and tell me why it can't be done that way.
First off, what kind of link are we talking about? If it simply opens a new mail in the default program (mailto: link), you're out of luck.
When you redirect to a page that is used to send the mail: