It's begun....

[JAZZCNC]

Do your self a favor and go buy Gerry's screen set here: The CNC Woodworker - Mach3 2010
Then make a simple touch probe plate from single sided PCB. Connect to a spare input and set the probe Input inside Mach to look at it.
Then enter the thickness of the PCB into the screen set and it will take care of everything else.
It will save you hours of time just with setting the Z height alone never mind all the other built in probe routines which will find corners, edges, circle centres, parallel edges best £15 you'll ever spend.!!

Oh and it has MDI on every screen which is priceless if like me you use it a lot.!!