Shipping hold, how to include outside services in the shipping hold and not just the direct customer

When I have a customer on credit hold, I can remove the production hold and allow the items to produce while I keep the shipping hold in tact. However, items I have produced that need to go to an outside service before they can be shipped to the customer are able to release to the outside service for shipping with the shipping hold on. The shipping hold is only preventing us from sending the product to the direct customer but not anywhere else. This creates an issue where we now have product complete, sitting at the outside service and the customer may not pay for a month. Any ideas?

Create a BPM to prompt a warning message when creating Subcontractor Shipment Entry.