Thanx! woprks very well now. This is what I ended up with.
M558 K0 P5 C"!io2.in" F100; create probe #1 for use with M585, active low
G38.2 X596 P0 G10 P2 L20 X0 G0 X{move.axes[0].userPosition-1} G38.2 X0 P0 G0 X{move.axes[0].userPosition/2} G10 P2 L20 X0 G38.2 y810 P0 G10 P2 L20 Y0 G0 Y{move.axes[0].userPosition-1} G38.2 Y0 P0 G0 Y{move.axes[1].userPosition/2} G10 P2 L20 Y0