I'm looking for some magic code to solve a small problem please!

I have a customer database where each customer can have multiple addresses. I have a dropdown list in the Add Customer form with "Address 1", "Address 2", etc.

On Edit, I'd like to indicate to the user which addresses have some data and which are empty. The way I see this is to add an asterisk to the end of say   "Address 2" in the dropdown list so that it become    "Address 2* ", indicating that address 2 has been filled.

I can see that I can add value to a dropdown list but in this case I wish to replace a value dynamically, and there's the problem. Any clues please?

Many thanks for any assistance provided!