I'm retrofitting Mach to a 1980 Fehlmann Picomax CNC mill-drill. Originally the machine was only two axes, but is now fitted with a stepper operating the quill feed. The original manual Z axis controls were quite sophisticated involving automatic spindle reverse for rigid tapping for example, and so the quill was already fitted with limit switches for the top and bottom of its normal operational travel. However, this machine also has a quick change tooling system which mechanically ejects the tool when the quill is retracted beyond it's normal "fully up" position. A second micro-switch positioned just above the Z-up limit switch was incorporated - presumably to tell the original CNC system that the tool had been changed.

If a picture paints a thousand words a video does even better - https://youtu.be/0v7gXR5AIKE - this is a manual P18 machine but the system is the same.

Since the position of the quill is now stepper stepper driven, I have a problem in that I can easily set up the two "normal operating travel" limit switches in Mach, but I don't know how I'm going to override the first top limit-switch in order to move to the second top limit-switch and eject the tool. Obviously, I want to do this as a manual command in order to make sure I'm present to catch the ejected tool-holder, and I also need to make sure that tool ejection can only take place with the spindle motor off (I will have the spindle motor under the control of Mach).

I'm sure that you clever people will think this is an easy problem to solve, but it's beyond a novice like me.