Leica CS25 hotkeys

I have a CS25 which has 3 function keys that I want to assign to letters (characters) so that when running my controller software I can click on one of the function keys and it would be the same as clicking on "M" for example, to take a measurement. In the controller software I can set the M and with a full keypad this works no problem. However with a CS25 the function kays are only able to run applications, batch files or other files. Does anyone know of a way around this, either by running a batch or creating a little exe or something - we have 25 controllers and this would speed things up immensely. I believe this is the same problem with the Trimble YUMA