I keep different types of data in different encrypted sparsebundle images (say, one for each client) which automatically mount upon login but can't be opened by anybody other than myself. So, after login I have a number of virtual volumes in /Volumes/ which keeps my client data both secure and organized.

How do I include data inside these virtual Volumes in TimeMachine's backups, or data residing in any path on any partition/volume?

I found a promising solution description at blog.eurocomp.info involving editing the com.apple.TimeMachine.plist but all I can get TimeMachine to do is backing up the sparsebundle files themselves. I want it to back up the files inside the mounted image, though - something like adding /Volumes/Client_abc/ to TimeMachine's search path.

Please do not redirect my to this previous question as it doesn't solve the problem at all. Please also refrain from telling me why you think I should not want this answer as that will not solve anything either. Please lastly don't say "it can't be done" unless you can technically prove that claim.