Merchandise Inventory Management

[eluser]skunkbad[/eluser]
Still working on my ecommerce system, I'm at the point where I'd like to integrate some sort of basic check to make sure items can't be oversold. Perhaps a check of cart items and quantities just before the credit card gets sent for authorization, and if quantities are no longer available, the user would get redirected back to their cart with some sort of alert as to what has happened. I don't think it needs to be more strict than this, but wondering if this just sounds like a pain for the shopper, and if there is a better way to handle it.

Also, perhaps some items could be designated as oversellable / back-orderable ....