I'm not using Mach3, but G code is G code right? The following might help if you can figure how to implement it.

I use a similar setter.
https://photos.app.goo.gl/sQkvtc2VG2aKBsb77

with this code.

Code:
o sub
;
G21 ( use metric units)
;  
G10 L20 P0 Z0       ( Set current Z position to 0 so that we will always be moving down )
; 
G38.2 Z-25 f150     ( Probe to Z-25 rough position seek )
G91                 (Incremental distance mode)
G1 Z2 f400          (Rapid Z up 2mm)
;
G38.2 Z-25 f25      ( Probe to Z-25 slow! )
G10 L20 P1 Z67.473  (set Probe position to the tool setter height)
; 
G90     (absolute mode)
G53 G0  (Use machine coordinates)
; 
G91     (Incremental mode)
; 
G1 Z25 f500 (Rapid Z up 25mm)
; 
G90(absolute mode)
o endsub