As most of you know, an xlsx file is actually a zip archive containing some xml files.

If you change the extension of the file from “xlsx” to “zip”, you can extract the content using a software like 7-Zip.

Once extracted the content of the file, you can make some modification and zip to get the xlsx file again.

But you have to pay attention: the files must be put in the root of the archive and not in the subfolder that you might have created while unzipping the files, otherwise Excel won’t open the xlsx file!