运行时错误'91'：对象变量或未在h = ie.hwnd行上设置块变量

Question

我在下面运行以下代码，但是在h = ie.hwnd行上出现运行时错误91。但是，当我在另一个模块中定义此变量时，不会出现此错误。我该如何解决该错误？

Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" _
(ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
lParam As Any) As Long

'Public Const CB_FINDSTRING = &H14C
Public Const WM_CLOSE = &H10

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" _
(ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, _
ByVal lpsz2 As String) As Long

Sub ClickSave() '(ClaimNumber As String)
Sleep 1000

Dim o As IUIAutomation
Set o = New CUIAutomation
Dim ie As InternetExplorer
Dim Completed As Object

Do
    Dim h As Long
    h = ie.hwnd 'Error on this line :(
    h = FindWindowEx(h, 0, "Frame Notification Bar", vbNullString)

    If h <> 0 Then
        Dim count As Long
        count = 0
        Exit Do
    Else
        Sleep 100
        count = count + 1
        If count = 50 Then Exit Sub
    End If
Loop
End Sub