Hi M When you create (or modify) a product, just next to the stock level you will see it is a select menu where you can choose to set the number "In Stock", or choose "By Options". If you choose By Options you set the stock levels in the product option you create. This does mean that you need an option per product. That is, if you have an option say, small, medium and large that you were using for lots of different items you now need to create a copy of that option per product so that the stock is only deducted when purchasing that product.
Hi Mxzrxp I'm afraid there isn't and the reason there isn't is because with all the different permutations of options it's not possible to check them before extracting the item from the database.