Saving line discounts in the Sales Order

To have the option to save discounts for the product line in the sales order as we go. One solution could be a pop up with a new discount overritten the old asking if 'user wants to overwrite exisiting discount'. 

This would cut down on a lot of admin and allows the system to remember any discount changes (% off list price) 

The process currently is –

• Create discount in discount reference book 
• Assign discount in the product for the customer 
• Apply discounts in the sales order.