Thanks Conor and jbrit,
I reckon Allow Checkout was probably always left at "true" since I installed this mod. The only reason this particular order caused problems for me was because he had been putting the order together over 4 or 5 days and I changed one of the items' availability in the middle of it.
Am I right in thinking that now that i've set it to "false" a php check will be made on the order,prior to checkout,and the customer (given these same circumstances) will be notified that the chosen item is now out of stock?
Yes, I do like the software Conor as a matter of fact my particular kind of business couldn't operate without it. A must have for shops that operate ON and OFF line and that have stock coming in and going out all the time.Cheers.