powerbook keyboard configuration

[farinet at arcor.de]

Hi you all!

Is there out there someone, who could guide me - or point me to a good 
instruction - how to configure the (my - GERMAN!) powerbook keyboard, to 
have access to the 3rd level chars (like square- and programmer 
brackets, at-sign, Euro sign etc. pp.).

I already tried 'dpkg-reconfigure keyboard-configuration' but to no extent.

 From former - partly successful - attempts i'm aware of several 
problems i'd well like to avoid:

If the <ALT> key is configured to acess that 3rd level signs, i always 
lost *ALL* other shortcuts relaying on <ALT> - like <ALT><F1> thru 
<ALT><F7> for console access and back as well as <AlT> shortcut 
combinations in lubuntu/openbox.

So, i'd prefer to have the right Apple/Window/Super_R key to work as 3rd 
level chooser.

'xmodmap' actually says:

----
shift       Shift_L (0x32),  Shift_R (0x3e)
lock        Caps_Lock (0x42)
control     Control_L (0x25),  Control_R (0x69)
mod1        Alt_L (0x40),  Meta_L (0xcd)
mod2        Num_Lock (0x4d)
mod3
mod4        Super_L (0x85),  Super_R (0x86),  Super_L (0xce),  Hyper_L 
(0xcf)
mod5        ISO_Level3_Shift (0x5c),  Mode_switch (0xcb)
----

Btw, which key or what is mod5?

Thanks a lot in advance for your patience!