Noniplot is BRILLIANT for this. I use it to mark trails when mountain biking, and you can even import trails to follow if you want to do some Geocaching.
Anyway, here is the link, I'm sure it's exactly what you requested. There is an option to export the trail you make into a google earth file, so you can just load it there.
Make sure you set the GPS com port to COM4.
http://aeguerre.free.fr/Public/Pocke...t/EN/index.php