Custom 404 for 1 folder

I have a customer who wants to track clicks on certain links in his own way. Basically he wants to mask where the link is really sending a person by going to his "special" folder on his site, counting the click, and then sending them on to the real site. It is affliate marketing and he is paranoid that people will bypass him if he doesn't mask the link to make it look like a normal link and not an affiliate link.

So he wants a link like http://www.hissite.com/dummyfolder/widgets.cfm but there is no widgets.cfm file. He wants it caught, parsed for the widgets, incident recorded in db, and then passed onto the affiliate site.

What I was thinking was have an application.cfc (or cfm) template that does everything since it is supposed to be executed before any other template but then I realized that there has to be a page in there or it doesn't process. Soooooo I'm looking at how to capture a 404 JUST in that folder and put everything in that template.

Any other ideas on how to do this?