About create a new signal for existing Widget

[Jiang XU <jiang xu echostar com>]

Hi, All,
            Is there a way to create a new signal for a existing Widget?

            Such as:  If I want to define a new signal, which is not an
existing signal (defined in GTK) for a GtkWindow, and put call back
function for that.
             Is there a way to do that?

                If somebody knows, please tell me ASAP, thanks very
much!