I'm not sure if it needs to change to the R1C1 format or what?
I tried "A1" and no luck,
Also tried A1:A17 range - still getting error

Can you take a look at NEW attachment (saved as xlsm)
Not sure how to put it in the R1C1 format

Also, I'm trying to get the result to appear in column K currently for the test
But will then move it into col B (so the formula in B will adjust based on the length of the filename in col A

Attached Files

test-paste-formula.xlsm (20.7 KB, 7 views)