Re-posting with my production community profile. . .
I think the easiest way would be to leverage the Munchkin API to record a 'Click link' event in the visitor's activity log.
For details on how to do it, you can visit this page http://developers.marketo.com/documentation/websites/lead-tracking-munchkin-js/
Look for the "Click Link" section under the "Calling Munchkin API Functions" heading.
Don't forget that you can invoke this like any other Javascript function. However, you must call the Munchkin tracking function Munchkin.init() before making any Munchkin.munchkinFunction() calls.
Here's an excerpt from the documentation on the type of call you would need to make:
Click Link
This call records a 'Click Link' event in the user's activity log. Use this when you want to record that a user clicked an Ajax, Flash, or other RIA link.
The href can be any value -- even a page that doesn't exist -- but the href must not contain "http://", domains, or URL parameters. The click link event will have the domain of the calling web page.
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Munchkin.munchkinFunction('clickLink', {
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href: '/MyFlashMovie/Story1'}
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);
I hope that helps.
Good luck!
Rafael