Not an easy task, but might be doable.
- Clik on Respond to Event
- Click on Advanced on any of your events
- Click on Create Advanced Event
- Name the event and specify Sunrise as event type, click add
- Now this event is in your list of events, and you can edit the criteria.
Now you might be able to limit the days to the weekdays to execute the scenario.
Good luck, and if it does work for you, PLEASE, either do a small screencast about it, and/or create a wiki page, so other people can do it as well.