Do you want to recover data from the formatted external hard drive?
How luckily you are. I know something about the recovery stuff since my brother has experienced the similar recovery problem before, just like you.
As I know, the data is not gone after the format. That's why one can recover it back. Therefore, you can try the hard drive recovery freeware that has helped my brother recover all his files from a formatted flash drive. You can visit this freeware here: http://blog4mark.blogspot.com/2012/12/deleted-files-rec... Another important thing: I hope you are so luckily enough that has not write new data on this drive to overwrite your wanted data.
Actually, in case of similar problem, you should back up your data all the time.