vba代码，画线为什么不显示，谁能分析下

<P>Sub yjt()</P>
<P>Dim pMXDoc As IMxDocument<BR>Set pMXDoc = ThisDocument<BR>Dim pScreen As IScreenDisplay<BR>Set pScreen = pMXDoc.ActiveView.ScreenDisplay<BR>Dim pPolyline As IPolyline<BR>Dim pRubber As IRubberBand<BR>Set pRubber = New RubberLine<BR>Set pPloyline = pRubber.TrackNew(pScreen, Nothing)<BR>Dim pLineSymbol As ISimpleLineSymbol<BR>Set pLineSymbol = New SimpleLineSymbol<BR>Dim pRGBColor As IRgbColor<BR>Set pRGBColor = New RgbColor</P>
<P>With pRGBColor<BR>   .Red = 1<BR>   .Green = 100<BR>   .Blue = 1<BR>End With<BR>With pLineSymbol<BR>   .Width = 2<BR>   .Color = pRGBColor<BR>   .Style = esriSLSSolid<BR>   <BR>End With</P>
<P>With pScreen<BR>  .StartDrawing pScreen.hDC, esriNoScreenCache<BR>  <BR>  .SetSymbol pLineSymbol<BR>  .DrawPolyline pPolyline<BR>  MsgBox "y"<BR>  .FinishDrawing<BR>End With<BR>   'pMXDoc.ActiveView.Refresh<BR>End Sub</P>