complose-key on sun keyboard

[Jan Menzel]

Hi all,
        as mentioned in section 2.4.2 (Modifiers and Mode_switch), lyx supports using 
the compose key. But on a sun keyboard exactly and and only insight the lyx 
window it does not work as described and expected. Typing Compose+"+U leads to 
a double-quote followed by a 'U' and not to Ü. Especially Compose+s+s to ß is 
necessary for writing German texts.
        How can I enable the compose key?

        Jan

PS: Please replay directly, I'm not subscribed. Thanks