The "security mask" parameter

[Mohammed_Maati at BIOGEN.COM]

I am using Samba version 2.0.6 and I need to use the "security mask"
parameter to prevent even the owner of a file from changing the read only
attribute
(by right clicking on the file from a  Windows NT 4.0 desktop) if the file is read only (Unix permissions: 0440). This is what I have in the
"smb.conf" file:
[global]
nt acl support = no
...
 [share]
...
 security mask = 0000
 create mask = 0640
 force create mode = 0000
...
But it doesn't do what I want it to do and which is what it's supposed to do according to the documentation.
Please help.
Thanks.