I think it would be fairly easy to whip up something like this with WebODF (http://webodf.org http://webodf.org). That is able to show real spreadsheet document

I think it would be fairly easy to whip up something like this with WebODF (http://webodf.org http://webodf.org). That is able to show real spreadsheet documents from software like Excel, LibreOffice, Apache OpenOffice and Calligra. Of course that works if you move away from the binary formats and choose OpenDocument Format - but this is default in most (and at least in Europe also one of the defaults of the latest two versions of Microsoft Office).