[VBA程序]：急：在VB中调用autocad2004打开一个dwg文件的问题

misters

请教：
用下面的代码，执行后
没有任何错误，也能打开autocad
但我要打开的文件不显示
只显示一个默认的drawing1文件
是怎么回事？
On Error Resume Next

Dim objacad As Object
Dim objdoc As Object
Dim mospace As Object

Set objacad = GetObject(, "AutoCAD.Application")
If Err Then
  Err.Clear
  Set objacad = CreateObject("AutoCAD.Application")
If Err Then
  MsgBox Err.Description
  Exit Sub
End If
End If

Set objdoc = objacad.ActiveDocument
Set mospace = objdoc.ModelSpace
Dim dwgname As String

dwgname = "d:\drawing.dwg"
If Dir(dwgname) <> "" Then
  objdoc.Open dwgname
Else
  objdoc.New ("acad")
End If
objacad.Visible = True
objacad.Refresh