为什么VBA运行时错误13开始DDE对话时键入不匹配

Question

我有此代码：

Public channel As Long

Sub Button1_Click()
  MsgBox "all is OK"

  ' Application.ActiveCell.Font.Bold = True
  channel = Application.DDEInitiate("Excel", "System")

  MsgBox "Conversation started"

End Sub

为什么DDEInitiate表达式给出错误13？