I use a program called Tyre.
It's quite easy to use.
The trick to getting the route you want is to add waypoints along the route, ie, just after turns to different highways along your preferred route.
Just right click the mouse pointer on the road you want to turn on and a prompt will come up "add waypoint" click that and go to next turn off & repeat.
You don't have to do it for every turn off, just enough to manipulate your route to your liking.
If you add a waypoint you don't want just click it and hit delete.
Play with it a bit and it won't take long to get the hang of it.
After you have a route you like, name & save it, plug your GPS into your computer (software works on Garmin or Tom Tom), top of the page you'll see "File" "Waypoint" and then either Garmin or Tom Tom which ever unit you are using, click that and then click send to GPS.
Here's the link to get the software, the free version is all you need.
http://www.tyretotravel.com/
There's lots of YouTube videos out there as well, just search tyre to travel...
