samba - Jan 2002 - Question on file locking

I am using Samba 2.0.7 as logon server. I also created a public share where
everyone can have full access into that directory. 

Is there anyway to make the server denied access (read, write, delete) from 
other clients to open file which has already opened by, let say, client1?

I have read and tried some possibilities on locking but don't work.

Any help is appreciated.

Thanks

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bpdp