Using Javascript and PHP to 'hide' links

[yahoo]

I've got a technical question, but it relates heavily to google.

I have paid for advertising at the top of my site. A simple banner with a link to the advertisers site. However, I don't want to pass on any PR or have google follow a link from my site to the advertisers (because I've noticed in the listings that the top ad shows up the most, and besides they are only paying for clicks, nothing else!!!!). Can I do the following without a problem.

Create a script called count.php which simply redirects the banner click to the advertisers site. So, for eg. count.php?id=4 would redirect to advertisers 4 site (with a mouseover to say http://advertiserssitehere.com/).

THen to follow up and make sure google doesn't follow it, put in the robots.txt file

Disallow: /dir/to/count.php