Sourcing Address Elements

In our business we work with customers, and our customer's customers, which we call 'end users'.

I have created a bunch of fields for the end user's address (Name, Add1, Add2, City, State, etc). Our vendors often require end user details when we place orders with them.

Occasionally, our customers will buy something to use themselves. In those cases, the customer and end user details can be the same.

To make this as easy as possible, I want to be able to copy the customer's address across to my custom end user address fields. I thought of doing this using a script and a custom button on the transaction, labelled something like 'End User = Reseller'. My idea was to go through each address element, and copy each one to the corresponding end user address field.