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What sort of help you do you need with planning directions?
And with what sort of GPS device (I would presume)?
Adding waypoints as you drive is dangerous and cumbersome, and highly inadvisable, I would say.
Do you mean, you want to construct a set of waypoints that define a route, and then replay the route through the waypoints on your GPS as you drive? that sounds more like nautical GPS procedure than on-land GPS procedure, but let me know what model of GPS you have, and I will advise you if it is possible or not... let me know more details, in short. Thanks.