Yo could use a 2 stream approach as I mentioned. That would mean that db user would take one approach or the other depending on what part comes in. Or you can stick with the current approach.
Either way, you can compare the values as in
?"AQ" > "AR"
False
?"AQ" < "AS"
True
and direct code flow accordingly. So if > AQ, skip out of the auto numbering (cancel the update) and present a message, perhaps.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.