Check out ControlGetPos..
$gui = GUICreate("", 300, 300)
$label = GUICtrlCreateLabel("", 10, 10, 200, 23)
$info = ControlGetPos($gui, "", $label)
If @error Then Exit
MsgBox(64, "", _
"Left :" & @TAB & $info[0] & @CRLF & _
"Top :" & @TAB & $info[1] & @CRLF & _
"Width :" & @TAB & $info[2] & @CRLF & _
"Height:" & @TAB & $info[3])