Set numbering properties (Numbering > Building Blocks) for the first instance to:
Set numbering properties for all others to:
Thanks Error - works great! BTW, how does one come up with 18279 equaling AAAA?
> ... how does one come up with 18279 equaling AAAA?
Well, I originally used trial and error, since I wasn't even sure that FM's A counter would do multiple "digits".
But the mathematical way is that "AAAA" is "1111" in Base26 (hexavigesimal / sexavigesimal). Any number of web calculators will convert that to Base10 (18279) for you.