Currently when an invoice has been raised from a Sales Order, those previously invoiced items turn grey on the Sales Order, but it is still possible to accidentally edit something on those items. Once one of those items is altered in any way, you then cannot save the Sales Order. This has caused us to have to scrap a lot of work on adding or changing other un-invoiced items, only to be told that the Sales Order cannot be saved. I understand it's our mistake in making changes to those previously invoiced items, but please please make it totally impossible to edit them. It would save us a lot of frustration. Thank you!