I want to generate an error if the incoming unit_selling_price differs from the pricelist price

My users want an order to get stopped by the Order Import process if the unit_selling_price on an incoming order line differs from the amount in the pricelist.

From my research and tests, if the calculate_price_flag is Y then the price from the pricelist is being used and the price on the incoming line is ignored.  If calculate_price_flag is N then the unit_selling_price on the incoming line is used instead and the pricelist amount is ignored.

I can't find a way to make the Order Import process error out the line if those 2 amounts differ.