How to quickly search a value in multiple sheets or workbooks

I've installed the macro to search for a text string in multiple closed workbooks (found at https://www.extendoffice.com/documents/excel/3354-excel-search-multiple-sheets-workbooks.html). It works fine to search for a text string in multiple workbooks in a folder. I have a big folder that contains folders that contain workbooks and I would like to search for a text string in all the workbooks in all the folders in the big folder. How can the macro be modified to do this?