I'm currently using this plugin to sell items that have a limited number in stock, and I'd like to somehow integrate a counter that checks when a PayPal purchase has been completed to subtract one from the total number on my WordPress db. Any ideas?
I'm currently integrating the plugin with NextGen Galleries and NGG Custom Fields, so I can have a field for each item that stores the number available. The only problem is, if I subtract one from the total each time the user clicks the "Purchase" button, there's no way to verify that they actually completed the purchase. What I'm thinking is that I somehow need to add a hook that listens for when the user completes things on the PayPal end. Is there a way to do this, or perhaps to add POST or GET info to the return landing page that can then be used to subtract the correct number of the correct item from the db?