I'm in a small company that has offices on the east and west coasts of America and also various people working from their homes. There are Windows Servers already in the offices. I think that Microsoft Windows DFS will do what I want, but despite reading the web site, I'm really not sure, so I'm hoping that someone can confirm if it will do all the following:

(For various personnel / political reasons I know that a proposal for a Microsoft Windows system has more chance of being accepted than any *nix system)

1. Creation of a Folder so that any files in this folder will automatically be available on the servers in all the offices.
2. When anyone opens up one of these shared files on any of servers, the copies on all the servers will automatically be locked. And when they close the file, the updates automatically get copied to the file on all the servers.
3. VPN access to these folders for people working outside the offices.

Bandwidth at the main offices varies from 6 Mb/s to 20Mb/s. Files are Excel / Word / AutoCAD ranging in size from 100KB to 4MB.

Thank you.