Detect a double key press in AutoHotkey

I'd like to trigger an event in AutoHotkey when the user double "presses" the esc key. But let the escape keystroke go through to the app in focus if it's not a double press (say within the space of a second).

How would I go about doing this?

I've come up with this so far, but I can't work out how to check for the second escape key press:

~Esc::

    Input, TextEntry1, L1 T1
    endKey=%ErrorLevel%

    if( endKey != "Timeout" )
    {
        ; perform my double press operation
        WinMinimize, A
    }
return