I’m not aware of a plugin, but you can embed an Excel Online spreadsheet into your website. I think I’ve seen Sage calculators that use this method. Here’s info on how to embed a spreadsheet from OneDrive: https://support.office.com/en-us/article/Share-it-Embed-an-Excel-workbook-on-your-web-page-or-blog-from-OneDrive-804e1845-5662-487e-9b38-f96307144081
Here are more advanced examples of embedded Excel ROI calculators: https://analysisplace.com/Tools/Example-Tools
