We need to display both Sales Order # and Reference (or PO) # on our invoices.

But unfurtunately we can't carry forward both the Sales Order # and Sales Order Reference # to our Invoices. 

To get around this, I've created a custom field in Sales Orders and Invoices that maps and displays well, but now I've got this useless "sales order reference number" field that still shows up when a staff members goes to create a sales order or estimate, causing and allowing human error.