Trying to set up Freight and Special Charges modifier

I have set up a freight and special charges modifier that applies a percentage to each line for Handling Charges and another for Insurance charges.  The problem I am having is that the price list on the sales order pulls in the item cost.  If the item is not in inventory at the time the order is placed, it returns a 0 price and the charges are 0.  Once I get the item into inventory I try to reprice the line and it does bring in the cost as the selling price on the line but the charges do not