This will depend on which GPS you have, some walking / hiking GPSs have a feature called Trackback (or Backtrack) which will guide you along a previously recorded Track, however vehicle satnavs usually work on Routes rather than Tracks, if the Route has been stored using Trip Planner then you can edit the Route to select a new Start and Destination, be carefull if you have added multiple waypoints in between the Start and Destination as the satnav may try to visit them in the wrong order