No lesson here, but I can surely point you in the right direction. In order to write code you need to learn to read it first. Start with the macros you use most often, print them out and run them single step mode on the machine. If you don't know what a command does, look it up and annotate that line with the description. A few passes thru your most common macros and you will be able to make minor mods, which in reality is what most people want to learn. If not, take my online class as it uses that exact method
Gary Campbell
CNC Replacement & Upgrade Controllers
Custom 9012 Centroid ATC