External drive incremental backups. Possible???

[davricho]

I have the following setup:

Imac which backs up via time machine to a 500gb Lacie external HD
Macbook Air which backs up via time machine to a 2nd 500gb Lacie external HD
1TB Time capsule which contains iTunes Library (Approx 600gb)
1TB WD Mybook external drive (to use for iTunes backup)

I'm trying to work out the easiest way to regularly backup my iTunes library which is held on the Time capsule onto the WD Mybook drive. I guess what I'm asking is there a program I can use similar to Time machine which will allow me to do incremental backups say once a week, rather than having to copy over the whole 600gb every time. I tried looking in Time machine to see if I could use it to backup an external drive but couldn't see anything.

Any help/suggestions would be appreciated!

 

[purelithium]

SuperDuper and the "smart update" feature. it scans the data in the source and target volumes and only updates what is necessary.

 

[davricho]

SuperDuper and the "smart update" feature. it scans the data in the source and target volumes and only updates what is necessary.

I've tried this, but the Time Capsule drive doesn't show up in the Source or Destination drive drop down list!