you must remember with a formula, you also have a link (since
something change in a book, your formula gives the new value)

If you need the value, you may evaluate the string, without writting
it first in a cell (vba function evaluate)

But, if this link is precious, the formula is probably the better way.


Whatever, you should look on the web the way to list a folder, so you'll
be abble to construct this formula with a loop (and not the explicit
names). I don't know the rest of the code, just a suggestion that might help