cookie installation

We are sending an email out to our database promoting a new product. We are going to have 3 different sales pages and would like to track what page works best. We will be sending about 10 sales emails over the period of a month and we would like to 3 pages to alternate each time one of our subscribers opens the URL. If the customer revisits the site we would like them to be sent back to the origonal page they visited the first time they opened the URL. Thanks