Is it possible to create a Multi-Year Purchase Order?

Summary

We need to create a multi-year Purchase Order that doesn't encumber the entire balance in the first year.

Content

We have a requirement from a supplier to create a 3 year purchase order.  Since the balance is to be paid over a 3 year period, we do not want the entire balance encumbered immediately when it is created as that would mis-represent our actual current year encumbrance/obligations.  Any thoughts on how to accomplish this?