Keycode, Itouch Logitech keyboard and KDE : How can I assign some keys with fonctions ?

I have a Logitech Keyboard Itouch with some key-functions like Volume, Switch Track, Launching Browser, Launching Mail Client.... After completing my /etc/X11/Xmodmap with Xfree variables, I am delighted to use Kcontrol Center to assign some of these variables to functions like launching evolution, Netscape, xmms... I know how to do that with sawfish but I did not see that on KDE 3.05. Could you advise me how to configure KDE in order to get the function-keys working ? Arnaud