Gift Certificates with pre-defined values

Former Member
Former Member $organization

We are creating a Student Season Pass. It will be administered as a Gift Certificate so that students can apply it broadly to chosen concerts. I know we can use a pre-defined value on the web but I am looking for a way to have the value be the only value available to box office users, to reduce errors. I have looked through the documentation but have not been able to find any thing. If any one out there has done this I would sure appreciate a little gudience.

Andy