Transparent Database operations

I am creating a top sites list for a specific industry group. This is kund of like a web ring but with a twist Should work like this: 1. members signs up through our form and we return a code fragment for their web page. 2. when the page is viewed, it will load and display a banner from my server, this is the easy part 3. When the banner is viewed, I want to record a hit on my sql database. This needs to happen transparently so as not to disturb the web site visitor. How can I make this happen?? Lance Earl