Hi,
if you are using a parallel port I don't think you can do it.
There is a difference between 'home offset' which is a Mach feature and enacted by the parallel port
and 'remote homing' which is not a Mach feature. There are some motion controller that can do it, the ESS
and the PoKeys 57CNC and maybe others too.
With a parallel port if you set a HOME OFFSET in the homing/limits page the axis will back off the switch, only
as far as it has to for the switch to change state, and then ZERO the machine coords for that axis if you have
not set a home offset, OR, set the machine coords for that axis to the OFFSET you supplied. IT DOES NOT TRAVEL
THE DISTANCE, IT JUST SETS THE MACHINE COORD TO THE OFFSET.
If you have a motion controller that allows it you can program a distance and the axis will back off that distance.
As I say I know the ESS and the 57CNC have it...don't know about the others.
You can get a similar thing to happen with a parallel port by specifiying offsets and THEN when hominig is complete
issue an MDI G28.
Craig