Advance Pricing Quantity Breaks

Hello,

We have advance pricing to give a quantity discount.  This works well during order entry.  One order was later split into two lines during commitment process (pick slips) and it kept the same correct pricing.

The issue we had came when after the order was split.  Customer service went in and made a date change to the lines.  This caused the system to recalculate the pricing and now since the line was split it changed the price to the non-discounted price.

Is there a way to prevent this or have the system recognize that these two lines should be added together for the discount?