as far as i know, this is a feature offered by Google Maps (and maybe some other online services). My plugin uses the OpenLayers API, and that doesn't offer routing services, so - sorry, no, i don't think my plugin will be able to handle this.
However, there are some other plugins in the Joomla Extension Directory that are able to do this:
Do you plan to include the feature of get directions in GPXTrackMAp ?
I mean: if someone wants to go to the beggining point of a track from a certain address/location would have a small form to input the data and witha click receive the GET DIRECTIONS.