tag the trap (based on criteria you set with the alert) with some text. Initially I would use something bizarre for testing like "catdog" or something.
the table it will reside in is the "Traps" table. an example query might be:
COUNT(tag) as occurances,
tag as TagName
group by Tag
that would simply give you this type of output for a query
I tagged 10 traps with "catdog" and I had a where clause limiting to 100. The other 90 were not tagged.
I'm willing to bet you could create a report in report writer natively without having to do the custom SQL, but I haven't tried.