Calculations

I am creating a form to track mileage and one of the drop downs has the most common locations with the miles listed. I set a binding for the miles as well. What I would like to do is have another box that will have the binding number appear. The table below shows what I am looking for. What would I need to do so that the Miles column auto populates with what is in the destination binding? I also have the destination dropdown as a manual entry so users can add anything else.

Thank you for  your help