Hi mate
Usually the NAS devices support other forms of file sharing, e.g. FTP.
You could write a little script that backs up your stuff nightly, it wouldn't take too much effort to do.
Could you post the model of the NAS? I'll have a look and see what it supports.
If you like I'd be happy to help write some scripts to do the backup, but I'm sure there's also plenty free software to do it too.
Cheers