[tor-relays] routing script

Hi, after having four entry/middle nodes online I would like to help out with an exit node. Unfortunately you will get in a lot of trouble in Germany for hosting an exit node. I spoke with an VPN provider and they are okay with routing tor traffic over their VPN as long I have exit rulez etc. The only thing I need is a routing script for Debian to route all the Tor traffic over the VPN. Anyone can help me out with this? Markus