For Excel 2011
Please download Microsoft Office for Mac 2011 14.7.2 Update and install it.
Please refer to the Install Instructions section on the Microsoft Download Center page for details on how to install a Service Pack.
For Excel 2016
To update Excel 2016, click on Check for Updates, which is located in the Help menu of your menu bar. A dialog window appears.
Click on the Check for Updates button. Please install any Microsoft Excel update if listed here.
The most recent updates will now be downloaded.