>Good point about needing not to forget the quantity on hand. But most likely the customer will update on hand quantity manually (adjusting the quantity).
>Thank you.

That was my point though. Would it not be better to have a fully fledged transaction for this kind of operation whereby you ask the user from which part he wants to move (or sell) how much (default to on hand) to another part (buy or manuacture). The advantage would be that it would be easy to audit. No?