The attendees would start populating their address with Google in the back end determining if the address is in their database.
If it finds a list it allows the attendee to select from the addresses that google has found. (screenshots)
If the attendee is already in the system their address would not show and they would need to add it using the selection during their registration
their address fields are greyed out and they must enter their data into the Address Verification field, once an address is selected it will populate the fields. (see screenshots)