Can you make hazel sync folder to external when connected

I want to setup my computer to backup copy a folder to an external hard drive automatically when the external hard drive is connected. Is this possible and how do you setup the rule?

Here's a link on how to use the sync action: viewtopic.php?f=4&t=1593#p6500

You shouldn't need to do anything special otherwise. If the drive is offline then it will fail and just try again when it comes back up.