E1 Standard invoice for Difference in Amount for an item in sales order

Hi,

Please advice if there is any way out to get the standard invoice for a difference amount for an item which is already invoiced partially to the customer & yet to bill for balance quantity. Scenario is as below -

- Generated the sales order for 100 Qty with unit price 10 each

- Partially done the shipment for  50 qty with unit price 10 each

- Generated the standard Invoice (R42565) for qty 10

- Now the Unit price got changed to 15 each

- So want to generate the standard invoice with original invoice reference no. for difference amount of 5 each against already shipped qty i.e. 50

This is the urgent requirement. Kindly do the needful soon.