Toggle Outgoing Fax Number when sending a fax

Asking if it's easy to toggle an outgoing fax number, when faxing back

Because all the clinics are a part of one environment, the users constantly receive faxes from external sources but to the wrong fax number. Therefore, they fax this fax using the correct fax number with a coverpage stating "future reference the upcc fax nubmer is [x] you've faxed dr sanghera's fax number".