Volume Incentives for a group of orders

We would like to utilize volume incentives to price orders sent from one customer sold to with different ship to's and different PO's.  These orders would come in via EDI and also be manually entered.  The customer will send or place orders for multiple ship to's with the same products on each order but different quantities in each order "bundle".  If there are existing backorders in the system from a previous "bundle" of orders and changes are made to an order that was entered in a different "bundle", we would need the system to adjust the pricing on the order