Shortcut to eject all external hard drives but not MobileBackups

So far I've been using the following AppleScript to eject all external drives at once conveniently using a shortcut: tell application "Finder" eject (every disk) end tell This script is is stored in /Library/Scripts and I have assigned a shortcut to trigger it in [FastScripts](http://www.red-sweater.com/fastscripts/) . But there's one problem. When you have **Time Machine Backups** enabled, OS X mounts a virtual MobileBackups volume in /Volumes to store **local snapshots**. This volume will be ejected alongside all the physical external volumes. I want to avoid this as this will stop local snapshots from being made (until it's mounted again at next login). ### How can I add an exception to exclude /Volumes/MobileBackups in the AppleScript above?