Hi Guys,
For some of you who are desesperately looking for the "Joker" program (link seems dead), here is an other small program which, I think, do the same thing
http://www-en.jtksoft.net/home
Work perfectly to assign my Joystick button to TAB key for muting in FSCrew, and the same joystick button is also used to send through FSUIPC to WideFS a command to activate the Push to Talk in TeamSpeak on a remote PC.
I hope this can help you :-)
Enjoy..
Patrick