Clives correct the basic code below doesn't need tip Dia to work.! . . . But this code is not safe and only has basic error checking.?

For instance it doesn't check to see if set to machine coordinates and warn the user or at least change on the fly and return when done.
The code gets the current value from WORK coordinate DRO and then adds +/- 75mm travel distance to variable which it then uses this value for G31 probe command.
If control set to G90 absolute coordinates before the probe is activated then will try to go to the value but in machine coordinates which could and will be very different to WORK coordinates.!! . . . . CRASH BANG SNAPPPPPP.