Set program zero using XY positioning laser

Hi all;

I've been converting from MACH3 to LCNC. In MACH3 I had configured an XY positioning laser using a macro that would allow me to jog to the program zero for a given project, then once positioned at the appropriate point I would click on a button that would calculate the X/Y offsets, move the spindle to the true program zero then set the G54 X/Y DROs to zero. This was very fast and accurate way to perform this task and along with a tool probe to zero the Z axis, program home is quickly established.

I would like to do something similar adding a button in the pyVCP to turn on the laser and once positioned a second button to compute the offsets, move the spindle to program zero, set the X/Y DROs to zero and turn off the laser.

Searching the forum, I've not found any info to work from. Has anyone configured a positioning laser on their system?  I'm a little rusty on my Python, but I can get back into it quickly or would classic ladder be a better option?  Any help would be greatly appreciated.

Kind regards

If I understand the BUTTON_1_CODE correctly, the G10 L20 P0 coordinate system is always offset to the fixed values defined by X and Y. How does positioning the cross-hairs to a difference starting position translate the offsets to the new location correctly?