Credit Card Surcharges/Debit Card Discounts

Hi,
I am looking to add a small fixed percentage surcharge for customers who pay with credit card through our site or, alternatively, to provide a discount to debit card users.

I have played around with discounts and it appears that a negative discount (to create a surcharge) is not possible.

I therefore created a coupon to generate a discount for a debit card payment.

This works fine except that it appears that any one order will only support a single coupon. However, I also need to use coupons for special offer products so it means I will not be able to offer the debit card coupon on those special offer products at the same time.

I'd appreciate any advice you can give for solving this problem.

Thanks
PhilP

Thanks for your suggestion Nicolas,

The custom code idea is definitely one for our developers to consider.

In the meantime, I think I can solve it by creating a choice of two shipping methods:

1. Delivery and payment by credit card (a fixed fee for the delivery and a 2.5% credit card charge)
2. Delivery and payment by debit card (a fixed fee for the delivery and no debit card charge)

I think this will do the job for the time being.

Regards
PhilP