samba - Jan 2008 - Different "Max Protocol" for different Clients?

How can I setup samba 3.0 to habe different "Max Protocol" settings
for
an Vista-Box and Win98-Clients?

For some reason Vista seems to work with "Max Protocol=lanman2" only.

For Win98-Clients this does mangle all long filenames, "Max 
Protocol=NT1" is required here.

Elmar