紧急求救：图层控制问题

我使用MO＋VB开发系统，当我用zoomfactor控制图层后，我的legend（MO的legend）就失效了，无法控制图层。请大家指教！谢谢！

<P>贴出来看看了</P>

<P>to：gis 我的源码如下：</P><P>Private Sub Map_BeforeLayerDraw(ByVal index As Integer, ByVal hDC As stdole.OLE_HANDLE)

' zoomFactor is the ratio of the current extent
' to the fullExtent
zoomFactor = frmMapDisp.Map.Extent.Width / frmMapDisp.Map.FullExtent.Width
'用于循环
Dim i As Integer
Dim j As Integer
' '存储图层名
Dim strLyrName As String</P><P>'获得图层名并进行控制性显示
For i = 0 To frmMapDisp.Map.Layers.Count - 1
strLyrName = frmMapDisp.Map.Layers(i).Name
Select Case strLyrName
Case "政府辖区"
frmMapDisp.Map.Layers("政府辖区").Visible = zoomFactor > 0.4
Case "警务辖区"
' frmMapDisp.Map.Layers("警务辖区").Visible = zoomFactor > 0.4
Case "绿化地"
frmMapDisp.Map.Layers("绿化地").Visible = zoomFactor < 0.3
Case "建筑区"
frmMapDisp.Map.Layers("建筑区").Visible = zoomFactor < 0.1
Case "道 路"
frmMapDisp.Map.Layers("道路").Visible = zoomFactor < 0.1
Case "道路中心线"
frmMapDisp.Map.Layers("道路中心线").Visible = zoomFactor < 0.1
Case "铁路"
frmMapDisp.Map.Layers("铁路").Visible = zoomFactor < 0.3
Case "桥梁"
frmMapDisp.Map.Layers("桥梁").Visible = zoomFactor < 0.3
Case "火车站"
frmMapDisp.Map.Layers("火车站").Visible = zoomFactor < 0.3
Case Else
frmMapDisp.Map.Layers(i).Visible = zoomFactor < 0.05
End Select
Next i</P><P>end sub</P>

可能放在Map_BeforeLayerDraw才有这问题，你可以看看放在其他过程里行不行

放在其他地方也是一样的效果