Thanks Will.
All my manual and the manual at docs.kde.org had to say about Behaviour an Notifications is 'Behaviour and Notifications covers the way Kopete integrates with your desktop, ?Away? settings, and chat user interface options.'.
For those interested, this is the command I came up with. It's even simpler than I expected.
echo %s | /usr/local/bin/mbrdico.dutch.female
Of course, this needs a speech synthesizer installed (in my case mbrola [http://mambo.ucsc.edu/psl/mbrola/]).
Also, I had to pipe the string through sed, to spell 'online' more phonetic:
echo %s | sed -e 's/online/onlaain/i' | /usr/local/bin/mbrdico.dutch.female
Rob