已经分配的Internet Explorer对象显示错误＆＃34; Object Required＆＃34;

Question

Private Sub CommandButton1_Click()
   Dim IE As Object
   Dim i As Integer

   i = 2
   Set IE = CreateObject("InternetExplorer.Application")
   IE.Navigate "http://www.mywebsite.com/Entry_Form.aspx"
   IE.Visible = True

   While IE.Busy
      DoEvents 'wait until IE is done loading page.
   Wend

   Do Until Cells(i, 1) = nil
      IE.Document.All("ctl00$MainContent$txtacccrop").Value = ThisWorkbook.Sheets("Sheet1").Cells(i, 1)
      IE.Document.All("ctl00$MainContent$btnsearch").Click

      Do Until Not IE.Busy And IE.readyState = 4
        DoEvents
      Loop

      IE.Document.All("ctl00$MainContent$txtfather").Value = ThisWorkbook.Sheets("Sheet1").Cells(i, 2)
      IE.Document.All("ctl00$MainContent$btnconfirm").Click
      i = i + 1

      While IE.Busy
         DoEvents 'wait until IE is done loading page.
      Wend

   Loop
End Sub

当第一次点击事件发生时，页面会加载新字段 ctl00 $ MainContent $ txtfather 。行显示错误

IE.Document.All("ctl00$MainContent$txtfather").Value = ThisWorkbook.Sheets("Sheet1").Cells