I've done some work where I've implemented some stuff in code that was originally done via excel formulas (some traders do things that way). I wrote some python to do symbolic substitution on formulas operating over many columns of data to reduce functions to single line definitions over just the data input, making my job much easier. Any programming language implementing the excel formula functions would make it super easy to automate taking prototyped multi-column excel functions to code.

There's a really nice XLSX reader and writer by Stephen Hardy, a Microsoft developer: https://github.com/stephen-hardy/xlsx.js/ blog post: http://blog.innovatejs.com/?p=24

I looked at that project but it uses a really strange non-free license that should be avoided. https://github.com/stephen-hardy/xlsx.js/issues/8