AllSync & AllDup

I am trying to do a backup of an external hard drive that contains
about 150 GB of data. I want to back it up to double layer DVD's. I have
calculated that this will take about 18-19 double DVD's. I have formated
24 DL disks. I started the backup process, but it stopped after the first disk
was filled. How do I get the program to prompt me when a new disk needs to be inserted? I don't understand how to get the backup to continue from where it left off.

How do I get the program to prompt me when a new disk needs to be inserted?

Sorry, this feature is not available.

Alternatively, you can use the zip functionality of the copy mode backup and create spanning zips with a size of your dvd media and burn them later.