Excel 2000 also accepts multiple worksheets as HTML. The Excel HTML specification is here, but it is easier to just save a workbook as HTML and duplicate the files (a HTML doc for the workbook, one for each worksheet, a style sheet and an XML file).

The HTML is a bit hairy but it would be an ideal candidate for HTML::Template or the Template Toolkit.

The above specification also details the Excel XML format.

John.
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Never trust a man in a blue trenchcoat, never drive a car when you're dead.