Why does this not get group ctrl contents id

[corgano]

I have this script:

$INTERNAL_USER32_DLL = DllOpen("user32.dll")
    Local $mPos = MouseGetPos (), $hWndUnder = DllCall($INTERNAL_USER32_DLL, "hwnd", "WindowFromPoint", "long", $mPos[0], "long", $mPos[1])
    ;this will get you the handle, from mats window finder tool
    $ID = _WinAPI_GetDlgCtrlID($hWndUnder[0])
    ;this will get you the ID

This will return the ID of any control, the problem is that if you have a control in a group ctrl then it only returns the group ctrl ID, not the controls it holds. How do I get the ID of a control in a group?