In SharePoint, if you have an Excel Worksheet in a Library, you can set it up so that it opens in the browser. When you do this, there is a link you can click which says “Open in Excel”.

Sometimes, you might get this error when clicking that button:
“To open this workbook, your computer must have a version of Microsoft Excel installed and your Web browser must support opening files directly from Excel in the browser”

If this error message appears, make sure you are using a 32-bit version of Internet Explorer and NOT a 64-bit version. This should take care of the problem.