Found it....
It has to be done in SpindleSpeed.m1s....
rpm = GetRPM()
pulley=GetOEMDRO(56)
If pulley=1 then
if rpm>500 then
Call SetOEMDRO(56,2)
MachMsg ("Change Back-Gear To High Range","Pulley Error",0)
end if
else
if rpm<500 then
Call SetOEMDRO(56,1)
MachMsg ("Change Back-Gear To Low Range","Pulley Error",0)
end if
end if
SetSpinSpeed( rpm )
Seems to do exactly what i want - pulley 1 would be low range, 50-500rpm and it warns me if the current set pulley is wrong, pulley 2 would be high range 500-3000 and it warns me to move machine into high range.
Nice