VB6 本地使用WebBrowser控件

Option Explicit
Private Sub Command1_Click()

    Dim d As HTMLDocument
    WebBrowser1.Navigate ("about:blank")
    Dim htmlstr As String
    htmlstr = "    "

    Set d = WebBrowser1.Document
    Dim flag As Boolean
    flag = False
    Do Until flag
       DoEvents
       If d Is Nothing Then
          Resume
       Else
          flag = True
          htmlstr = htmlstr + RichTextBox1.Text + "

"
          d.body.innerHTML = htmlstr
          d.body.Style.background = "url(E:/xxxx/111/src/bh_image.jpg)"
       End If
     Loop

 End Sub

Private Sub Form_Load()

    RichTextBox1.Text = "ABCDEF"

End Sub
在d = WebBrowser1.Document的时候总感觉取实例不一定成功,还有错误提示，所以就循环了一下，就能取到内容，这是为什么？