Adding confidentiality message at bottom of each email

How does one append a confidentaility message at the bottom of each email sent?

I know how to set up a signature, but that goes at the end of the message and prior to any prior messages that are included. I do not want the confidentaility wording to go after the signature but at the very bottom of the message - where everyone else's confidentiality wording goes.

I am using LIon 10.7.3 and Mail 5.2.