Epicor 9.05 Calculating Available Qty

Can anyone tell me how Epicor 905 calculates Available Qty for a part in inventory? In Vantage we calculated it by:

PartWhse.OnhandQty - PartWhse.AllocQty

In Epicor 905 the Partwhse.allocqty field no longer exist but now there is a field called Partwhse.allocatedqty but in our database this field doesn't appear to be used in regards to what is allocated.

Any help on this would be appreciated. Thank you

Robert Nupp