Random Sponsor Ad on Thread Title / Link

[ThePimp]

I'm looking for a javascript or a plugin of some sort that does the following:

The script needs to alternate between the actual thread title / link on the forumdisplay and a random link specified in a short list somewhere. So, essentially, there should be a 1:100 chance that they get a sponsor ad instead of a thread.

I doubt this is a difficult thing to do, I'm just not too proficient w/ Javascript or using PHP in vBulletin yet.