How to default customer on budget adjustment based on offer

Currently in 12.1.3 for budget adjustment for EARNED amount we need to enter a customer, but system will allow you to enter any customer on this adjustment screen and also this is a required field to adjustment. Is there any way to default the customer name based on the offer selected on this screen OR avoid it as a required field for doing the budget adjustment for earned amount.

Please advise. I also opened a SR but this is NO functionality available to avoid it but look forward for a work around to resolve it.

--Sam