数据绑定错误

<P>我的代码如下:</P>
<P>procedure TMainForm.Button2Click(Sender: TObject);
var
  lyr:Cmapxlayer;
  unusedParam:olevariant;
  sSqltext:String;
  ds: MapXLib_TLB.Dataset;
  flds,fldsline:CMapXFields;
  EmptyParam,fields: Variant;
begin
  TVarData(unusedParam).vType := varError;
  TVarData(unusedParam).vError := 2147614724; // DISP_E_PARAMNOTFOUND;
     fields := CoFields.Create;
     fields.Add('GEONAME','GEONAME', miAggregationAuto,miTypeString);
     fields.Add('tfcalls','tfcalls', miAggregationAuto,miTypeNumeric);
 // ds:=map1.Datasets.Add(miDataSetADO, ADOQuery1.recordset, unusedParam,unusedParam, unusedParam, map1.layers.item['cover'], unusedParam, unusedParam);</P>
<P> ds:=map1.Datasets.Add(miDataSetADO, ADOQuery1.recordset, unusedParam, unusedParam, unusedParam, map1.layers.item['cover'], fields, unusedParam);
  ds.themes.add(unusedParam,unusedParam,unusedParam,unusedParam);
 // ds.Themes.Add(miThemeRanged, 'tfcalls', '掉话',unusedParam);
end</P>
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<TD  width="100%"><IMG src="http://www.gisempire.com/bbs/Skins/Default/topicface/face715.gif" align=absMiddle border=0> <B></B>
我绑了半天，图层中的字段也建了索引，layer图层有一个字段和数据源的某一个字段匹配，,可还是出现这样的错误——InValid GeoField specified. Name not found, or index out of range. ，为什么啊？？
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