Вот так работает:
Код:

#include <IE.au3>
$oIE = _IECreate("www.autoitscript.com")
$oImgs = _IEImgGetCollection($oIE)
For $oImg In $oImgs
If $oImg.Alt == "Download AutoIt" Then
$iScreenX = _IEPropertyGet($oImg, "browserx")
$iScreenY = _IEPropertyGet($oImg, "browsery")
ControlClick("[CLASS:IEFrame]", "", "Internet Explorer_Server1", "Main", 1, $iScreenX, $iScreenY)
EndIf
Next