Creating an eccomerce site for a client. They have 2 products which can only be purchased by people who have attended their training classes. When they attend, they are given a paper with a VERY generic serial number... lets say ABC-12345678. Ive used an input mask to hide the cart66 add to cart button, so that someone has to enter at least ABC-12 and then the cart button appears. This doesn't have to be secure, just enough to hassle people who don't have a real serial number.
My question is, is there a way to validate the first 3 to 5 characters in the serial... So that someone must input ABC-12345678 and something like DEF-98765432 will not work?