Rather than use the native Excel libraries consider writing to Excel via Open Office XML, not pretty or easy but does not require Excel to be installed.
Another option is to use a wrapper library which uses Open Office XML like SpreadSheetLight which is free or a paid for library from Gembox or Aspose.
Our team builds web and server base solutions, started with Open Office XML then moved to GemBox as it's much easier than writing Open Office XML. Don't have any simple code sample for Open Office XML, we did away with that code.