Customer Open Orders as of specified Date

Anyone out there have an idea of how to create a report that would give the Sales order Deliver remainder and Remaining net amount of open orders for a specific customer as of a particular date in the past?

You would have to calculate it, if today we load an order and in a week ship it, then run teh report with todays date the deliver remainder would be 0 so we would need to look at the shipments and any shipments between the date and today add into the deliver remainder - nothing as standard would give this to you to my knowledge.

Thanks, thats the approach I figured I would end up having to take.