Hi RGraham
I have heard of a way by placing a rocker switch on the wire that senses movement of the vehicle. This is done before the wire enters the multimedia system, which will then "trick" the nav system to thinking you are stopped. this worked well on my previous vehicle Pajero, but I haven't yet had it done on my few months old VX. Go and look on UTube, as I saw something there that was interrupting the white wire feeding the nav system.
Good luck.