It would probably be simpler to do something like UPDATE CounterTable SET Counter=Counter+1 when you do an INSERT. You can find the changes by selecting with the clause ORDER BY auto_increment_field DESC or ORDER BY creation_date_field DESC, and reading as many records as the difference in Counter since the last time you checked.

Caveat: Some databases allows you to specify value for an auto-increment field. You can't use that feature if you want ORDER BY auto_increment_field DESC to work.