Excluding future orders from credit checking

How can we exclude orders from credit checking where the orders are for items in the future?

For example a customer creates wants to place an order in a magazine every month for the next 6 months. We create 6 orders and interface to Oracle OM. ie. Jan order, Feb Order, March order etc.

However we would like to only include the orders which are for adverts in the next 30 days in the credit checking. That way the future orders do not impact the customers available credit if he places a second order in January.

We need a way that credit checking constanly is only checking the orders for adverts in the next 30 days.