I don't get my extended keys running...

1. I start xev to spy the keycode of my keys (e.g. Back = keycode 234)

2. now I activate the keys using >$ xmodmap -e "keycode 234 = XF86Back"

3. In KControl I enter the this key as second shortcut for b ack

4. In Konqueror I try this new setting.
- My Back key doesn't work as shortcut!
- The other shortcut "Alt + Left" works properly.

Any ideas what to do to get the key workin?