gridview输出excel ，如何指定路径，急？

下列代码，如果想指定输出路径，如何做
         Response.Clear();
        Response.Buffer = true;
        Response.Charset = "GB2312";
       Response.AppendHeader("Content-Disposition", "attachment;filename=FileName.xls");
     
        // 如果设置为 GetEncoding("GB2312");导出的文件将会出现乱码！！！
        Response.ContentEncoding = System.Text.Encoding.UTF7;
        Response.ContentType = "application/ms-excel";//设置输出文件类型为excel文件。 
                   System.IO.StringWriter oStringWriter = new System.IO.StringWriter();
        System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
        t.RenderControl(oHtmlTextWriter);
      
        Response.Output.Write(oStringWriter.ToString());
       
        Response.Flush();
        Response.End();