[MSFT] employee here. Among many other things, we've announced today, we talked about Excel REST APIs. This API allows you to access and modify Excel Spreadshee

[MSFT] employee here. Among many other things, we've announced today, we talked about Excel REST APIs. This API allows you to access and modify Excel Spreadsheet. This may do what you’re looking for. There are more details at http://dev.office.com/blogs/build2016release http://dev.office.com/blogs/build2016release. (about half way through the page). Hope this helps.