Jasko - thanks for that. I have tested this with my own machine and it works fine. Because all my home switches are connected to separate inputs on the CSMIO, I home Z, then X/Y/A simultaneously. To do this, my button script is:

RefCombination(4)
RefCombination(11)

Note - I use X+A as my dual axis. However, this script would work with Y+A as well. I home Z first to ensure that the spindle is at maximum height to avoid hitting anything while the other axes are homing.