how to export particular sheet in web application

private void ExportToExcel(string strFileName, GridView dg)
  {
      Response.Clear();
      Response.Buffer = true;
      Response.ContentType = "application/vnd.ms-excel";
      Response.Charset = "";
      this.EnableViewState = false;
      System.IO.StringWriter oStringWriter = new System.IO.StringWriter();
      System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
      oHtmlTextWriter.WriteLine("<font size="5"><font color="blue"><center> REPORT </center></font></font>");
      GridView1.RenderControl(oHtmlTextWriter);
      Response.End();
  }