I have a submit button on a form that I'd like people to NOT press more than once since the backend of our server takes a while to process the form sometimes. People tend to click on the button 2X or more. Is there a way to have it so a popup window pops up and tells them not to click on it more than once? I'd like to have it say something like, "Slow the hell down buddy! There's no need to click on this twice."

Thanks for the help in advanced.