How can I recover data that was overwritten by time machine?

I have a 2 TB external hard drive on which I had archived a lot of video and data files. I hooked it up to my MacBook Pro thinking that I could also utilize time machine.

It asked me something ot the effect of "Would you like to use this drive for time machine" (I don't really remember what it asked), but I clicked on 'yes' or 'continue' or whatever and before I knew it, it had erased my hard drive and backed up my MacBook Pro.

Is there a way to recover that data?

With fingers and toes crossed.......thanks for any help.

Mark Rabalais