form to populate orders list sourcing customer list

 
i have two lists: Customers and Orders
 
i want to create a form that populates Orders list but sources the Customers list to get Customer_ID
 
The catch is that i want the user to choose from a list of customer names and have but to have the form return customer_id
 
an example of this is html drop-down boxes. they can be created to show one value (eg customer name) but return another value (eg customer_id)
 
im certain there must be a way to do this in sharepoint but have found no reference to it.
 
-Dave