Bill of materials problem

[physixz]

Hi, I'm still in the middle of deploying a new solution for the company I work for. We are a manufacturing sub-contractor and we use filemaker for most of our systems such as orders, products and stock etc but I am rebuilding the system in a new database whilst adding new features. The bit I'm stuck on is the our Bill Of Materials (BOM) for a product contains a list of the stock codes of components that are used to build it. The stock codes are ideally created and all of the information entered and then locked so they cannot be changed since they will be on many products, but if there is a typo or a mistake then it will need to be updated. Ideally I want the BOM's to look and show the current information on the stock code when we generate a pick list to build the item but show a message when you come to print the list that a stock code has been updated and somehow have the option to view the last values ie when the BOM was created. My tables have not real data in so schema changes aren't a problem. Anybody have any suggestions?

My current design in the image allows me to have the BOM show the stock code value as when it was originally created.

Product - shows portal of BOM's with revisions

BOM - shows portal of lines