Include Parent Table Fields in DropDown Form

Include Parent Table Fields in DropDown Form

I know there must be an easy answer to this:

I have 3 tables with the following fields:

Customers - Fields(First_Name, Last_Name, Phone)
     Jobs - Fields(CustomerID, Job Name)
          Billings - Fields(JobID, BillingAmount)

The relationships are one customer to many jobs and one job to many billings.  When I enter a billing entry, there is a dropdown for Jobs to select the JobID and the values that can be shown are limited to the fields in the Jobs table. Is there a way to include fields from the parent table Customers in the dropdown display for Jobs? Ideally what I would like to see in the dropdown would be Customer Last_Name and then Job Name.