I'm the query engine:
"hey, there are 2 fields with the same name in the design grid and yeah, the creator has specified which is which there, but which one of them is supposed to provide the value in the Len function??"
HTH

FWIW, I was not the first to point that out, but I did expand on it when I seconded the notion in post 6.



EDIT - second look, I see what you're getting at. Frankly, I cannot recall ever having that problem since I can't recall ever duplicating field names. If I did it was long ago and probably soon learned about ambiguity. I don't think the expression can "see" your intentions because there is the optimizer and engine for the query but there is also an expression service which, IIRC, does not "see" what the query engine sees. I may not be using the correct terms there - I'm a bit rusty on things that don't raise issues for me. The ambiguity is often the cause for table/field references in vba generated sql and you might experience that one day. It's something like "Too few parameters. Expected: x"