When the outputs (and which ones) turn on is in the POST of the CAM program. For example the POST for SheetCAM to MACH for plasma triggers OUTPUT 1 on after the XY postion moves and after a Z move to a pierce height. That would come close to what you want by doing rapids at Rapid Height, move to the start point, lower the head to a "pierce height" (which would be your cut height) fire the Laser and start moving. It turns the output off at the end of the cut and raises to rapid height and does the process all over. You need to select a CAM program that will let you control your toolpath and cut process and output proper g-code for MACH.
TOM Caudle
www.CandCNC.com
Totally Modular CNC Electronics