DHTML code using JAVASCRIPT

I need a DHTML window to come when somebody presses the back button of the web browser. The code should be written in Javascript. The DHTML window is allready designed. All I need is a script where the DHTML window will come when the back button is pressed. Please note that the script should be designed in such a way that there should be no confirmation message coming from windows operating system. If you bid on the project I will send you the exact website address where we need this. To see a sample of what a DHTML window is and how it works you can go to the following website: [login to view URL] As soon as you land on the page there should be a window with google search. This is a DHTML window.