Magento Stock Control

I want my magento to deduct store only when the order is invoiced. I have store credit module and customer can placed order with internal credit or offline payment. The order that fully paid by internal credit will be invoiced directly. Some orders that placed with offline payment will be invoiced manually. I would like Magento to deduct the stock only when the order is invoiced. If I create credit memo for my order, the stock will return to the inventory automatically. I wish you can download all the data and do the changes and test it in local. When everything is ready, then only sync to the live site.