Script for page timer/expiration? A page that has its own expiration (eg. 24 hours)

I would like to know a script for when you have a page that can expire (or cannot be open again) --- a time limit for like 24 hours.

Because I'm going to make a site where people can buy website designs, they buy it off paypal, they get redirected to a site where the code is located and the site will get expired in 24 hours -- then, they wouldn't be able to open the page again.

If anyone knows the script, please post it here! Thank you x

This will have to be done serverside

You create a random url code that will generate a page. You store the code somewhere (database). Each time the code is used you check against the database whether or not it exists and has expired. If it hasn't expired you show the page, otherwise you delete the code from the database.