Manual Shipping Question

On my current website I offer free shipping for orders over $90. This was easy enough to setup in CS-Cart. The problem is that when I offer a discount coupon to a customer, lets say 10% off, the free shipping is applied based on the original subtotal without subtracting the coupon. I need it to take the discounted subtotal for use on determining to give free shipping or not. In other words an order that is $95 before the coupon and $85.50 after would not get free shipping.

If anyone has made this alteration to their cart please let me know. I’ve looked at the code and I know where this takes place, it just doesn’t have access to the discounts on the order in that function and I figured I’d ask here before I rewrite the shipping code.