Thanks for the tip! I was doing some work translating some Excel calculations that used Excel's IsError function and the Mid function. I had already replaced all the IfError functions in Access, with a combination of Iif and IsError, and was still getting the same #Func! error. It turns out, the Mid function in Access does not return a true error in the same way Excel does, but a zero, which kind of make sense but that was completely messing my original logic which as I mentioned came from Excel. In the end, I substututed this

Iif(IsError(Mid(Afield,Start,End)),AlternateValue,Mid(Afield,Start,End))

with this other formula

Iif(Mid(Afield,Start,End)=0,AlternateValue,Mid(Afield,Start,End))

This is a much more compact and easier to understand formula in Access, and it actually worked! All thanks for your answer that took 6 years to figure out! It is now another 6 years in 2024 when I am reading your comments, it is now my time to give something back. Thanks you very much!