How do you implement the discount for a product. We are using standard fields for discount (% field), quantity (number field), list price & unit price. However, we have a custom field for "annual sales price" (formula - unit price*term*quantity)

The unit price should ideally be modified by the (list price*discount) then subtract that number from the list price. Then, the sale price will correctly reflect the discount if there is any. Any thoughts on how to implement this?