MS Document with Samba Changes Owner of File

When user B saves a MS document that is owned by user A, the updated file is now owned by user B, and user B saves the file again, the permission reset to owen read only. How do I fix this?

        force create mode = 0770
        force directory mode = 0770
        force security mode = 0770
        force directory security mode = 0770

These two settings will ensure that all directories and files that get created in the share will be readable/writable by the owner and group set on the directory itself.

http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/AccessControls.html