I'm not sure this is possible. Does the Flash Player Plugin, or Safari or Firefox actually record when the plug-in is accessed. I'm thinking it doesn't. If not, I don't know how you would run such a report. You need something to go on, even for an EA script.
For kicks, I took a look at what Spotlight had to say about the Flash Plugin in /Library/Internet Plug-ins/ and unfortunately, unlike regular apps, there is no launch or access history recorded there. Maybe there's a log that captures that, but I've never seen one.
At least in Safari I know Flash runs as its own process so theoretically you could write a daemon that looks for the process with ps and tracks it however best fits your needs