Detect Change made from outside of ws

Hi folks,
I know this detect change in a cell kind of thing has been around in a lot of threads but I think this one is different. And I could not find a solution yet, whatsoever.
In Column A is data that is taken from another excel file (just copied). That other excel file is being changed by users due to new inputs. Since the data in Column A is linked to that other excel, it changes itself. This change I want to detect.

The worksheet_change doesnt work, since there is no actual change done by the user.

At the end, if I can detect this change I want to keep a different column synchronized with column A. Is this possible at all?

Thanks for any suggestions!

So do I have to assume, that this is not possible?