Wanna Download single excel file with Multiple tabs.the Output desired output in attched in from of image

Question

Code iam using is HTML table and it is downloading a single excel file only

_String.Append(" <table border=\"1\" style=\"border-collapse:collapse; padding: 4px; margin: 3px; font-size:10px; font-family:Times New Roman; text-align:center;\">");
          _String.Append("<tr>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc; \">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none; border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none; border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none; border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none;border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none; border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none; border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border-bottom:none;border-right:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");

            _String.Append("</td>");
            _String.Append("<td style=\"padding: 4px; margin: 3px; border:solid #ccc;\">");
            _String.Append("&nbsp;");
            _String.Append("</td>");
            _String.Append("</tr>");
   _String.Append("</table>");

Download Logic :

Response.ContentType = "application/x-msexcel";
Response.AddHeader("Content-Disposition", "attachment;filename=ExcelFile.xls");
Response.ContentEncoding = Encoding.UTF8;
Response.Write(_String.ToString());
Response.End();