I have a similar problem in that I provide a service (temporary staffing) and my customers will sometimes create a purchase order on their end for my services.  For example, they wish to allocate $50,000 to temporary personnel for a specified project.  My invoices to them need to reference their purchase order, and we would like to run status reports, or better yet, receive an alert when we have completed the majority of the purchase order and may need to approach the customer to either increase the current PO or create a new PO.  Is there a way to manage this in Quickbooks (using Desktop)?