#include <Misc.au3>
HotKeySet('{ESC}', '_Exit')
$iClicks = 0
While 1
If _IsPressed(1) Then
While _IsPressed(1)
Sleep(10)
WEnd
$iClicks += 1
EndIf
If $iClicks = 2 Then
$iClicks = 0
MsgBox(64, @ScriptName, 'Second click!')
EndIf
Sleep(10)
WEnd
Func _Exit()
Exit
EndFunc