Ghost and backup from external drives

I have a NAS where 4 persons of my family put their documents in order to make it possible to access these from all the computers in the network without having to synchronize.

Offcourse I want to make a backup of these documents. Is it possible with ghost installed on one of those computers to make a backup from a directory-structure on the NAS to the computer which initiates the backup? If not, are there other products which I can use to make this possible?