Put this script on your crontab:
#!/bin/sh
/sbin/mount_smbfs //username@server/share /Volumes/share
cd ${HOME}/Documents/
find . -mtime -1 -a \! -type d -exec cp -rp {} /Volumes/server/username/Documents/ \;
It mounts a server share that you know gets backed up, finds all your files that got touched today, and copies them to your directory on the share.
Set it and forget it.
