I'm in a similar position with engraving tezt. What I do is to place my part to be engraved and manually jog the table to where I want the engraving to begin, I then zero the DRO's and look at my Gcode in the program window and program the X, Y and Z axis to what the readout of the Gcode says. In other words, the start of the program may call for X-0.125, Y0.00, Z0.200. I'll enter those values in the DRO's and then run the program. It works well for me but I'm sure there is a better way. To get to the Z axis to 0.0, I'll manually turn it down by hand with a cigarette rolling paper ( I bought a case of 5,000 of them for 4.00) between the tip and the part to be engraved. When the paper is "caught", I call it zero. Again, it works for me but I'm sure there is a better way. MAch3 is an extremely powerful program and I'm probably using only a small percentage of it.