Automatic e-mail scheduling mod

Hi all, I want to set up a card shop with CubeCart 4. But one mod I need before I can do this is as follows. A customer orders a "card of the day" and after they place the order, they will receive by e-mail once a day, a new card. (some mod which connects to the database and randomly selects a record from the COTD table. It then scans for the users in the database and determines which users need to have the COTD sent to them. ) I know I can use Cron (scheduling program in linux), but I don't know how to set it up. I will also need it to run off time zones for the customers to get it just after 12.00am. If anyone knows of a mod or if they can build one of me then let me know. Thank you all for your time. Mike D.