remote desktop only works locally

view full story

http://askubuntu.com – here's my problem, I want to be able to remote control my grandparents computer in order to help them without having to drive 20 minutes to get there. however I can only connect to their machine when I'm on the same network. I'm using the default vnc server vino with vinagre client.what settings do I have to use to make it work? (their os 10.04.4 , mine is 11.10) (HowTos)