How Do I Know if I am Running 32-bit or 64-bit Excel?

Office 2019 down to 2010 offer native 64-bit versions. XLS Padlock is an add-in for Excel, so it must match the same bitness as Excel.

In this article, Microsoft explains how to find the version and bitness of your Office installation

For instance, for Office 2016: start Excel. Open the File menu, and then select Account and click About Excel: