Help needed assign joystick button for iFly 737 NGX

Already posted in the excellent iFly forum but no response so maybe not possible,I want to make a Joystick button assign to switch between the 2 Comm radio'sI am using Fs2Crew voice commander and can give only the voice command to set a freq. on Comm 1 and Comm 2 and that is the F/O side and not workable for me.The goal is to change Freq. by voice to keep my eyes on the track in a non precision approach and not to look down on the pedestal to set a standby Freq. and handling the switch to do the Freq. change. I tried to figure it out with FSUIPC but no success.The iFly gives tons of keyboard assigns but for as far I can see no Joystick assign dispite the fact that I also haven't discovered the correct keyboad assign as a last resort to do the job.Happy landings...