inventory widget: how to keep track of quantitiy

In creating my form, I would like to control the inventory in such a way that a product that is out of stock will indicate as such.  Right now, even when i set the quantity to 1 - the item can still be ordered.

You can use the inventory widget. Just search for it on the widgets tab (left hand side). And drag one widget per item. 

Here's a demo:

https://form.jotformpro.com/72066926258969