Debug osCommerce order total problem

This is a snap for anyone who is familiar with how the order total module works in oscommerce. I just don't have the time to sift though the code. I need help debugging an osCommerce store that I setup. 1) It is using payflow pro as its credit card module, and another module called "category tree discounts" that gives a discount based on number of items bought. 2) Everything works fine, except for the fact that when you use payflow as the payment method, it charges the non-discounted price. 3) It sends the correct order total to oscommerce, and it will send the correct order total if you use paypal, or check/money order as the payment method. Needs to be done in the next week.