Small ajax amendment

I have a website with a custom made cart system that has an option to enter a discount code. Usually customers receive $20 off. We want to use this same method but have a code that gives them a bonus with their order and not a discount as such. Once the code is entered and checked, it shows in the cart that the code has been recognised but does not take any amount off the order total. It also removes the option to enter a second code, this it already does but it need to remain in place. I need this done today if possible. all of the ajax for the normal discount code is in place and works great. I dont think this is a difficult task when so much of this is in place already. Previous coder who did this for me is too busy this time to help. Thx