Transition to Commission Plan Using Alternate Sales Amount

We are looking to transition to using Alternate Sales Amount for Gross Profit calculations for both inventory and non-inventory items for purposes of commissions.  We want to pay the commissions on a mixture of booking & collection (e.g. 25% on booking / 75% on collection) using marginal rates.  Question: when the sales order is approved, does the total ASA get written immediately and only payment of the commission is deferred OR does a partial ASA value associated with the timing of the booking get written and another partial value associated with the timing of the collection (i.e. sales person would