I am looking for a type of payment module that will do the following and I want to know if it exists or if someone can point me in the right direction (if a custom-written plugin is needed so be it):

Using Zen-Cart's built in coupon discount feature, we would like to offer customers the ability to "donate" their discount to a charity of their choice.

How this would work (in my mind) is:

a) The customer recieves a coupon giving them 10% off their total purchase. The enter in this coupon code and it re-calculates the total, giving the 10% discount.
b) Either in-the cart, or at checkout time, they can choose to "donate" their discount to a charity - thus the 10% discount would go to the charity instead.
c) The total purchase price of their order would revert back to the "un-discounted" price for them, but we would somehow track that, $3.00 (as an example) just got donated to the Red Cross.

This obviously has a need to provide accounting for the fact that a donation was just made to a specific charity.

I've found a few similar plugins out there, but nothing quite like this.

Any suggestions??

Thanks much!
-= scowby =-