Eric,
In you have SAP ERP 6 EH6 or 7, selected APO functionality is available as an addon.
The functionality of confirming sales documents based upon the availability of components exists as standard in APO Global Available to Promise. It is called 'Multilevel Available to Promise' (MATP).
For more info about MATP, check out this topic in help.sap.com.
Best Regards,
DB49