I initially created this to improve my C# understanding and what a learning curve it was. So I decided to directly translate the C# source code I had into AutoIt as a way of showing off the >Stack UDF (which you will need). Of course it can be changed not to use the Stack UDF, but why reinvent the wheel and make life even more difficult.   If you don't understand RPN or the Shunting-Yard algorithm, then please look at the links below.   Sources: https://en.wikipedia.org/wiki/Shunting_yard_alg