formatting event list widget with li classes …

I would like to be able to apply some design / formatting to the events list widget. I can define some internal li elements in the widget code but the opening ul and li elements seem to be generated by the php and have no class applied.

I can edit widgets/em-events.php directly to resolve this but this will get overwritten on any update.

I’ve also tried following same principle as templates by copying em-events.php to themes/mytheme/plugins/events-manager/widgets but this does not over-ride the base file.

So how can I add the classes required to apply css styles to the initial ul and li elements in em-events.php without having them all overwritten on a plugin update?

Many thanks.

http://wordpress.org/extend/plugins/events-manager/