Create an Excel file from AS/400 or ASP
It is possible to create a file that Excel likes without being an actual
Excel-formatted file. The trick is to create a HTML file, but named .xls.

A template for creating the HTML file:
(html xmlns:x="urn:schemas-microsoft-com:office:excel">
(table border="1">
  (!-- insert table rows here -->
(/table>
(/html>

Example file excelhtml.xls:
(html xmlns:x="urn:schemas-microsoft-com:office:excel">
(table border="1">
  (tr>
      (th>Product Id</th>
      (th>Description</th>
      (th>On Hand</th>
   (tr>
      (td align="left"> WIDGET-A</td>
      (td align="left">A Widget</td>
      (td>0</td>
   (/tr>
   (tr>
      (td align="left">WIDGET-B</td>
      (td align="left">B Widget</td>
      (td align="left" x:str="'00225">00255</td>
   (/tr>
(/table>
(/html>
 
Notes:
. Using the <td align="left" x:str="'00225">00255</td> format creates
  a numeric field with leading zeroes, equivalent to typing '00025 in a cell.
. Creating a <th> row will automatically boldface the headings, just
  as it does in HTML.

Ps: sorry for the '<' changed to '(' - but the code render itself as HTML code 
and wont show up as text (Think400.dk)