I've *heard* the possibility of D-Link adding rsync to the DNS-323 but that doesn't really help you out in a Windows environment. Of course you can also accomplish this with ffp, but that's outside the scope of this forum.
Let me make an observation, however. The DNS-323 itself does not have the ability to be a host-initiated backup device. The clients (i.e. your computer(s)) need to initiate the data transaction to the DNS-323. Most NAS are designed to be a target to store data to, not initiate backup jobs. That is what software and/or servers are designed to do. BackupExec, GFI, and Acronis True Image work in this fashion.