There is a small utily that I used ( in the same way as Checkpoint) ie. running on top of the main nav program, which in this case was TomTom. It was called "ukpostcode" would you believe !, and was written by a Guy called Niels Thomsen of digitools.co.uk.
You could open it with a dedicated PDA button while the nav program was running, enter a postcode on an OSK, and sellect "show on map" OR "navigate to".
It worked seamlessly with TomTom, and presumably a similar program could work in the same way with Powerloc.
Don't know if that helps anyone ?
Car : Ford Focus Zetec S 1800cc
Carpc :Galaxy GT-P1000 Original 7in Tab
Mounted in "On Dash" Custom Install