material determination with ATP-CHECK.

I want use the material determ after the stock ATP-CHECK.

the need detail is that:

first the sales order item run the atp-check ,if the stock cannot supply all the requested quantity ,the shortage quantity will use the material-substitution,by the choose screen or automatic create the new item.otherwise,if the stock is enough to supply,not to run the funciton material determinaton.

this is the all my want,whether is it can be carry out and how to configure the sap setting.