Hi,

You cannot do that without forking the code and I recommend never forking the code. However if you are a developer experienced in asp.net it is not very difficult to implement your own custom contact form starting with our hello world example. 

Otherwise, you could also consider purchasing Form Wizard Pro, it has built in support for tracking form submissions in google analytics, though it doesn't track it as an event but as a pageview using an url that you define in settings, ie /myformwassubmitted this custom url is sent to google analytics only upon completion of the form separate from page view tracking that happens for regular views of the page without form submission.

Hope that helps,

Joe