samba - Oct 1999 - Setting Read-only attributes from Win95 on FreeBSD

Hi,

I have installed a FreeBSD-based samba fileserver for a customer
and discovered belatedly that they make extensive use of setting Read-only
attributes on the old NT server.  All of the client machines are win9x.

There are many users which need access to the files in question, the group
permissions are set, with all files and dirs set to mode rwxrwx--- (770).

The problem arises in that the customer has a requirement that the files
be set read-only or read-write by any user who has read access to the
file, or read write access to the directory.

I've discussed the security models with senior staff at the client site
and they definitely want this function, or things like strict-locking in
their RCS software won't work to their satisfaction. 

Is there anything in Samba currently which will provide this
functionality?  Is it likely to be difficult to modify samba to do what I
want?  I'm prepared to modify the FreeBSD kernel to get this
functionality, and I've been looking at sys/ufs/ufs/ufs_vnops.c. 

Any help at all would be appreciated.

Thanks,

Danny