我的插值代码错在什么地方

<P>我的IDW插值程序在运行时，总是出现下面错误：“The cell size is either invalid or not defined” <BR>栅格大小我改了很多值都出现一样的错误，我觉得我的代码没有错误，希望高手能提点以下。   <BR>   Dim pFeatClass As IFeatureClass<BR>   Set pFeatClass = pFeatLayer.FeatureClass<BR>   Dim pFDescr As IFeatureClassDescriptor<BR>   Set pFDescr = New FeatureClassDescriptor<BR>   sFieldname = Combo2.Text  '字段名<BR>   pFDescr.Create pFeatClass, Nothing, sFieldname<BR>   Dim pGe As IGeoDataset<BR>   Set pGe = pFeatClass<BR>   Dim pE As IEnvelope<BR>   Set pE = pGe.Extent</P>
<P>   Dim pIntOp As IInterpolationOp<BR>   Set pIntOp = New RasterInterpolationOp<BR>   <BR>   Dim pRAE As IRasterAnalysisEnvironment<BR>   Set pRAE = pIntOp<BR>   pRAE.SetExtent esriRasterEnvValue, pE<BR>   Set pRAE.Mask = pGe<BR>   <BR>   Dim cllsize As Double<BR>   cllsize = 31 ‘栅格大小<BR>   pRAE.SetCellSize esriRasterEnvMinOf<BR>   <BR>   Dim pRasterRadius As IRasterRadius<BR>   Set pRasterRadius = New RasterRadius<BR>    <BR>   pRasterRadius.SetVariable 12<BR>   <BR>   <BR>   Dim pGeoDataset As IGeoDataset<BR>   Set pGeoDataset = pFDescr<BR>   <BR>   Dim pOutRaster As IGeoDataset<BR>   Set pOutRaster = pIntOp.IDW(pGeoDataset, 2, pRasterRadius)<BR>   <BR>   If pOutRaster Is Nothing Then<BR>      MsgBox "DB"<BR>      Exit Sub<BR>   End If<BR>   <BR>   Dim pRaster As IRaster<BR>   Set pRaster = pOutRaster<BR>   <BR>   Dim pWSF As IWorkspaceFactory<BR>   Set pWSF = New RasterWorkspaceFactory<BR>   <BR>   Dim pWS As IWorkspace<BR>   Set pWS = pWSF.OpenFromFile(Text5.Text, 0)<BR>   Dim pRasterDataset As IDataset<BR>   <BR>   Dim pRasterBc As IRasterBandCollection<BR>   Set pRasterBc = pRaster<BR>   Set pRasterDataset = pRasterBc.SaveAs("Raster", pWS, "GRID")<BR>   <BR>   Dim pRasterLayer As IRasterLayer<BR>   pRasterLayer.CreateFromDataset pRasterDataset<BR>   Form1.MapControl1.AddLayer pRasterLayer<BR>   <BR>   Form1.MapControl1.Refresh<BR></P>