Advanced Pricing Rebates

I have a base price set up in the system and multiple adjustments based upon that price. The base price is highest price charged and is rarely used. A major customer may have an adjustment of ADJ90. This will produce a 10% discount of the base price. I am setting up rebates based upon sales volumes. The percentages are based upon the net price and this works well. However, I need the sales volume to also be based upon the net sales amounts. Is there a way to do this?

For example:

My base price is $100 for item X. This item has never been sold for $100.