My folder topology looks like this:
main folder -> containing 44 folders -> each of them containing 1-3 specific folders -> where each of those specific folders contain 1 specific folder -> which contains the xlsx-files (about 10-30 files) which need to be converted into xlsb-files.
So the 44 subfolders contain around 1800 xlsx files?
Is the "1 specific folder" in the subfolder named the same?
Is that 10-30 files in each "1 specific folder" or all up?
Do the files that need converting have anything in common. eg tag, dates?
Can you do a search in Explorer and return those specfic files or sort returned files so there grouped?