Take the following example…
A gallery owner sells one-of-a-kind artwork within his high-street store and on-line through his website. As an item can be bought in person or on-line, there is the possibility that an item may be sold before the store owner has the chance to remove the item from the website.
What would be ideal is a purchase process along the lines of:
1) A customer browses the website and adds items to their basket.
2) On checkout, the store owner is notified of the customers interest in the selected items.
3) The store owner is then able to confirm if the item is still available and, if so, reserve it for the customer.
4) If the item is available, the customer can then pay for the item using the normal payment gateways.
Does that sound at all possible?