The best way to do this is to create a VPN to your host's network. Otherwise, you either have to edit the registry from a full radmin session - something you clearly don't want to do - or setup some very strange port forwarding on a router.
Some routers support the VPN function and come with client software to allow you to connect at will. I know that D-Link has some sub-$100.00 routers that do this. Not sure about all of the rest.
As an alternative, you could implement an Microsoft VPN tunnel between the two computers.\
All of this can be a bit complicated. Here's a place to start:
Here is the official MS thread about remotely administering Windows machines:
Of course, most of what MS lists there doesn't work unless you have a direct connection, or VPN, to the network. Remote registry editing is NOT soemthing that's easily enabled through firewalls on purpose. Imagine what would happen if it was easy to do? That's why I recommend a secured VPN, or just connect to a radmin session and do it locally.
Hope that helps somewhat. Post the exact O/S's that you're trying to remotely administer (regedit) and maybe we can come up with a more specific solution.