Error with innerHTML property set

[aproximator 0]

I try to change innerHTML property with code below

$oIE = _IEAttach ("Booking")
$oFrames = _IEFrameGetCollection ($oIE)
$iNumFrames = @extended
For $i = 0 to ($iNumFrames - 1)
    $oFrame = _IEFrameGetCollection ($oIE, $i)
    MsgBox(0, "Frame Info", _IEPropertyGet ($oFrame, "locationurl"))
    $str = _IEPropertyGet($oFrame, "locationurl")
    If $str == "http://mysite/schedule.php" Then
        $HTML=_IEDocReadHTML($oFrame)
        $oF = $oFrame
    EndIf
Next
$formHV = _IEGetObjById($oFrame,'formHV')
_IEPropertySet($formHV,"innerHTML",String($formHV.innerHtml) & '<input type="text" readonly value="test value"><BR/>')

But I am receive error message:

D:\AutoIt3\Include\IE.au3 (3450) : ==> The requested action with this object has failed.:

$oTemp.innerHTML = $newvalue

$oTemp.innerHTML = $newvalue^ ERROR

Somebody knows how to decide this problem?

P.S. Forgive me please if my question is foolish.