Suggestions :
Use Sales order amendment to create amendment to the existing ‘open’ orders. As in the case of order, an amendment document is also sent to the customer. The order, if required, can be re-amended for any number of times but the order is always referred to with its original number in all the transactions.
Users can change the rate in Sales order amendment for the items added in Sales order. Secondly the items should be active which we are in Sales order for which the rate needs to be altered otherwise the system will show a validation message ‘Inactive item, Item not active hence cannot be ordered’. Users can enter the rate at which item is sold, as per amendment.