Thank you for this beautiful programming demonstration. This complex
exercise did more for me
than going thru my collection of VBA books or filtering the postings
on the subject here,
like calling Excel functions etc... I will go back at it, again and
again until I master logic & syntax.
That being said and trying to refine the application further,
1. How would I implement at the beginning of the run, whether to be
prompted for unknown codes or
or have the program simply write them to an Exception table, thru
your Temp_Code_Table()

2. Variation : With an additional table of Codes that are no longer
allowed to be used.
How would I write those Periods attemps to use them and the
unknown or new codes to the Exception Table ?

3. In range definition, what drives using either End(xlUp) or
End(xlDown) ?
Thank you again,
Celeste