Macro to open and close all files in a folder and sub folders

Hi JBeaucaire
Thanks for this, but it doesn't seem to go through the sub-folders, it will cycle through and Excel fils in the top level, but doesn't seem to go into the sub levels

The set up is around 4 sub folders with about 10 files in each, there are no other sub folders lower down, these 4 all sit in the original top level