Help! 怎样将CAD的Dwg文件转到mo中(VB)

<P>下面是代码，但运行不了，错误提示为:</P>
<P>实时错误‘91’
对象变量或With块变量未设置</P>
<P>代码为：
</P>
<P>Private Sub Command1_Click()
Dim lyr As New MapObjects2.MapLayer
dc.Database = "[CADArea]C:\CAD"
Set lyr.GeoDataset = dc.FindGeoDataset("Drawing1.dwg")
If lyr.Valid Then
lyr.Symbol.Color = moRed
lyr.Symbol.Size = 3
lyr.Symbol.SymbolType = moLineSymbol
Map1.Refresh
Map1.Layers.Add lyr
Else
MsgBox "null"
Exit Sub
End If
End Sub</P>
<P>Private Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
Map1.Extent = Map1.TrackRectangle
Else
Map1.Pan
End If
End Sub</P>
<P>Private Sub Form1_Load()
Command1.Caption = "显示CAD文件"
End Sub</P>
<P> <IMG src="http://www.gisempire.com/bbs/Skins/Default/emot/em12.gif"><IMG src="http://www.gisempire.com/bbs/Skins/Default/emot/em12.gif"></P>

<img src="images/post/smile/dvbbs/em07.gif" />