How to make Customer Account Parameter on Create Balance Forward Bills ESS Job as mandatory

Summary:

We have a requirement where we are using Balance Forward Billing feature in Receivables. To generate a bill, we need to run the ESS job - "create balance forward bills" with parameters. In that we have From Customer Account Number parameter which is optional but we want to make that parameter as Mandatory. Can you please let us know if you have come across similar requirement and how you achieved it?