Syncing with external hard disk

I have bought a external hard disk. I want to use it as a shuttle between work and home.
Here is what I want to do:
1. I want to work on my office machine and sync the files to the external disk.
2. Go home and work on the external disk directly changing and updating files.
3. Go back to work and update the files on the office machine that have been changed at home.

Here is the opensourse software for that…….DirSync Pro from Sourceforge.

http://sourceforge.net/projects/directorysync