Backing up FROM a NAS device

I'm probably missing something obvious but I'm happy to make myself look silly if someone can supply an answer. A friend was using Acronis 2009(?) as his backup software which worked well until I set him up with a needed NAS service using Freenas. What I then needed to do was set up his backup routine to now backup the data on the NAS device to an external HD attached to his PC. His then version of Acronis failed to find the device and so I've been testing using the current trial version of Acronis 2011 which does see both device and data and a full backup is comfortably created. However, try as I might, I can see no way to set up an incremental backup as all I can see when I try are his local PC drives. If someone can point out where I'm being dense and how to do this I'll be very grateful (and Acronis will then get a sale).

TIA

Jabod