[Plugin: Event Calendar 3] Show only events using hardcoded calendar?

Anyone know how I might be able to alter the <?php ec3_get_calendar(); ?> which I use to hardcode the small calendar of upcoming events into a sidebar so that it only displays events from a category ID?

At the moment, it shows my events but also marks every blog post as an event too.

I’m not using it as a widget because I need more control over my sidebar with some other custom bits so if anyone can help tell me how I might be able to show only entries from category ID 3 (for example) using the php snippet above I’d be very grateful!