Is there a way to set up a shared extension that is displayed and rings on 2 or more phones, without setting up a group?

We have several users that telecommute several days a week. I have a VPN tunnel set up and working. I need a simple solution to have their office and home phone both ring so we dont need to keep track of where they are on any goven day.

We have a Panasonic KX-TDA 100 system using KX-T7630 and KX-NT136 Phones.