Mirroring Folders/Files on drives

I have a number of folders and files on an external drive that I would like to mirror in iCloud. My definition of mirroring: putting a folder in iCloud Drive and on an external drive where both files will update if I were to make changes to any file.

Here's what I have set up.

• I have an external drive with with a large folder containing subfolders for documents and photos.
• I have a copy of that folder on my iCloud Drive for those instances when I do not have my external drive with me and as a backup to my external drive should it fail for some reason or gets lost.
• I occassionally will add something to one of the sub-folders on my external drive.
• I want that item to be added to the same sub-folder in iCloud Drive.

Can I do that and if yes, how?