How to default sales agreement on sales order

I want to use sales agreement functionality to stop products from being ordered; however, I don't want to use the release functionality to process orders.

I would like the sales agreement number to automatically default on an order when a place an order for that specific customer on the sales agreement all the time.

However, I don't see where I can make that default in the defaulting rules for Blanket Number - Related - Sales Agreement.  Is there anyway to always have the sales agreement # default on a customers orders when they are just placed via Order Management?  Thank you.