samba - Aug 2005 - How to set up a time limit?

Hi There,

We use Samba 3.0.1prel-1, Openldap 2.0.27-8, Redhat 9 and Windows xp.
I want to set up a time limit for users to log in, that is when the time 
is up users can not log in any more.
How to do it? Is it anything to do with the sambaKickoffTime attribute?

Thanks in advance,

Richard