Try this script and please test this in the air.
Zpos = GetDRO(2)
Code ("G31 Z" & Zpos -1.00 & " F10.0") 'Probe down one unit
Zpos = GetVar(2002) 'Get the point where the probe hit
Code ("G00 Z" & Zpos) 'Rapid to where the probe hit
while Ismoving()
Wend
Call SetDRO(2,0)'Set the Z to zero
Thanks
Brian