If I understand what your asking there is no easy way to do it that I know of. When you double click Tk sees the first click and calles the code bound to the <Button-1> event, at this point from Tk's perspective there has been no double click. When the second click of the double click is recived the code for the <Double-Button-1> is called, but the code for <Button-1> will already have finished at this point.
The only hack I know to get to recognise that a click event is the first part of a double click is to scedual a sub to be called in about half a second on the first click event and then set a flag on double click (or unscedual the sub and call a different one) that lets the sub know that it was called in a double click. If the flag is not set it's a single click.