Since you can get to machines in the LAN from home, all you need is screen sharing software (Timbuktu, VNC or Apple Remote Desktop, they'd all work) on each. You make a connection to the VPN, start up a remote control session with a "master computer". Then that one starts a remote control session on the computer with the dongle that you need to tweak. You're effectively working through a middleman computer to control the real destination.