[Samba] file locking

[Pramathesh Ambasta]

I am sure this is a subject which has been discussed a lot already. I have 
been looking for pointers but have failed. So please bear with me and help.
A linux box runs Samba and is connected to a win box. One word or excel file 
is opened simultaneoulsy on both (on the linux system in OpenOffice and on 
the win system in M$Office). How do I prevent simultaneous writes on both 
machines? What I want is that one system gets r-w access and the other read 
only.
Is this a samba issue or is it an issue which the application program must 
address?
I have enabled strict locking and disabled oplocks.
what more do I need to do?
Grateful for help
Pramathesh