Okay, the mod that you recommended does the calculations that I want to achieve but it applies the discount automatically based on subtotal, which is not what I want.

I want the discount to be applied ONLY when a particular payment method is used. This mod found here: http://www.numinix.com/zen-cart-modu...ent-module-fee does what I need...but it only offers a specific percentage discount (i.e. 25% across the board) or a flat rate discount (i.e. $10). I want it to calculate a tiered percentage discount, just like the way the price sensitive mod works (i.e. 10%:$100, 15%:$200, etc.).

This mod that is referenced calculates automatically without having to worry about the check box option.