heh benson, didnt see your reply.
I doubt any calibration can be setup or will be required since depending on how much you roll your thumb it drifts slightly anyway.

Its taken me so long to get this idea out because I've not thought about it for a while, the touchscreen on my primary nokia is knackered and does not respond to finger touch (main reason why i did not write any working test code) and it wasn't until the summit that I obtained a device with a working screen