synchronized file use across internet
 

My boss wants a system for backing up files across the internet from out office to his house, we were going to get static ip's and dsl at each location and place a linux server at each location. I was going to have it just backup the files from the office tot he alternate location every night at 8pm or something, but now he wants to be able to use his laptop at home like he does here to work on files (autocad files)

now I need to make sure if a file is changed ont he data server on one end it is instantly synchronized on the other end. as well because it is autocad files on a multiple user environment we need to make sure only one person can access a file at a time, autocad will normally lock out a file when it is using it to prevent others from using the file, however I need it to lock it out at both locations.

I was thinking I could make the main location here at the office share with nfs then the other side use the nfs for his laptop (the server on his end will mount the server at the office with nfs, then share the nfs mount with his windows laptop over samba) then backup the main server at night when nobody is using it (nobody will be using it after 8:00pm) but I am not sure if the samba shareing of an nfs mount across the internet would uphold the autocad file lockouts...

any ideas on a better way to approach this, or if anyone knows if my idea will work?