A way to create a text field of all the sub-folders that an item is in?

Knowledgeable help on this would be much apprciated

I need to create a text folder/column that concatenates all the 
sub folders that an item is in. As an example I have something 
like the following folder structure

Categories (text)
  Name1 (check mark)
  Name2 (check mark)
  Name3 (check mark)

So for an item that is in Name1 and Name3 I want the 
Categories column to show "Name1, Name3". For another item 
that is in Name2 and Name3 Categories would show "Name2, 
Name3"


Is there a rule that would do this?  There's no way to use the 
'Column Properties/Sub-folders that Contain Item' as the values 
are not accessible as text.

Many thanks in advance,
David

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