If the Lock Unit Price field is checked on the sales order line, then when the quantity on the sales order line is changed, the value in the Unit Price Excl. VAT field is not updated - the sales price is not retrieved again according to the set rules and this current valid sales price is added to the sales order line.
If the value in the Unit Price Excl field is modified on the sales order line. VAT and at the same time the unit price is locked, then a message will appear asking if we really want to update the line and unlock the unit price - see the picture below.
