>>>Type Field Name Criteria Value
>INNER TABLE2.Catalog = SUBSTR(TABLE1.Catalog, 1, 5)<<
>
>Yes, but what I can't figure out is where on earth I add this code when I'm using the View Designer.

You would place the code in the 'Value' listbox of the 'Join' tab in the View Designer. I tried to show that with the various listbox names above the code (Type Field Name Criteria Value), but the spaces I put in to separate the listbox names got compressed and didn't line up with the code underneath.

Having read Cetin's response (which was news to me - I learn something new every time I visit the UT) you may not need this, but...