将EXCEL文件数据导入ACCESS数据库的原代码？

procedure TForm1.Button1Click(Sender: TObject);
var
  OpenDialog:TOpenDialog;
  iCount:integer;
  filename:String;
begin
  if MessageDlg('是否真的导入Excel数据？',mtConfirmation,[mbYes,mbNo],0)
      =mrYes then
  try
    openDialog:=TOpenDialog.Create(self);
    openDialog.DefaultExt:='xls';
    openDialog.Filter:='Microsof Excel 文件(*.xls)|*.xls';
    openDialog.Execute;    if openDialog.FileName<>'' then
    try
      fileName:=ExtractFileName(OpenDialog.FileName);
      Screen.Cursor:=crSqlWait;
      ExcelConn.Close;
      ExcelConn.ConnectionString:='Provider=Microsoft.Jet.OLEDB.4.0;Data Source='+openDialog.FileName+';Extended Properties=Excel 8.0;Persist Security Info=False';
      Excelconn.Open();      With ExcelQuery do
      begin
        Close;
        SQl.Clear;
        sql.Add('select number,name from [Sheet1$]');  
        //上面一句改为sql.Add('select number,name from [filename]'),也出现同样的错误
        Prepared:=true;
        Open;
      end;      iCount:=ExcelQuery.RecordCount;
      ADOQuery1.Last;
      Excelconn.BeginTrans;
      ExcelQuery.First;      while not ExcelQuery.Eof do
      begin
        with adoCommand1 do
        begin
          CommandText:='Insert into xsjk values('
            +''''+Trim(ExcelQuery.FieldByName('Number').AsString)+''''+','
            +''''+Trim(ExcelQuery.FieldByName('Name').AsString)+''''+')';
          Execute;
        end;
        ExcelQuery.Next;
        form1.StatusBar1.Refresh;
        statusbar1.Panels[1].Text:='当前数：'+IntToStr(ExcelQuery.RecNo)
          +'(共'+IntToStr(iCount)+'条）';
      end;      ExcelConn.CommitTrans;
      MessageDlg('数据导入成功！',mtInformation,[mbOK],0);
    except
      ExcelConn.RollbackTrans;
      MessageDlg('数据导入失败！',mtInformation,[mbOK],0);
    end;  finally
    ExcelQuery.Close;
    ExcelConn.Close;
    OpenDialog.Free;
    screen.Cursor:=crDefault;
    StatusBar1.Panels[1].Text:='';
  end;end;//上面ExcelConn为ADOConnection组件名，ExcelQuery则为ADOQuery.但该程序运行时
显示：project1.exe raised exception class TDatabaseError with message"Missing
Connection or connectionString.".请问我的程序中，哪里出错呢？ 谢谢！！