Metrics on Throttle Plugin

I'm interested in knowing how many times a particular key was throttled. I've been poking at this problem for the better part of a week now and the only thing I have been able to come up with is being able to determine if an event is throttled or not.

Am I missing something really obvious?

Thanks in advance!

You may need to use the filter before the throttle one to get an idea of total through put, then again after to get a count at that point, then compare.