Need something like referral and counter.

Hello,

I am basically new to Drupal and don't know much php also.

I have made a custom node (CCK) which collects information from students willing to apply for a summer project. Some of them can be sponsored, some of them can't. Those who are awarded by their teachers would be given a code they can enter in order to authenticate and participate without paying, the others just submit the form with empty code field. What I need to do is make some kind of counter that subtracts 1 every time somebody fills the form with sponsorship code. I also need to display the number of sponsored positions that are still available in the form or somewhere else. And finally I need to disallow sponsored submissions if there are no positions left, but others can still apply for regular attendance.

I've researched for some time but I still have no solution how to do this. There's no referral module that can do this. The user referral module works for users that register to the site, but I need the form submitted by users that are already registered.

Any ideas how can I do this are welcome!

Thank you in advance!
Kacho