As the title may hints, I have a spreadsheetML file that I would like to convert to a binary XLS (native MS-Excel format).

The main problem is, that I need to put some graphics into the excel file, which is not supported by the spreadsheetML specification. The spreadsheetML is xsl transformed from a XML source. I could now generate the XLS from the XML source in code, but thats not so neat. I would rather just pipe the generated spreadsheetML file into a postprocessor that adds graphs as I want it.

I would welcome also a FO-processor that can write binary XLS files because I could, if I would, just create FO and render these into XLS using a strict subset of the FO specifications.

Any ideas, libraries etc how this could be done? Please nothing that is GPL based, the Apache license is fine for me.