Event Types - flexible slots

We often have service events that occur almost daily over a period of one to two weeks, that allow for flexible shift attendance.  Most commonly, such an event will occur 10 am-12 noon (break for lunch) and then pick up again 1-5 pm.  We need volunteers who can volunteer for 2+ hours in the day or over a period of days.  They can come for whatever 2+ hour period they are available.  This type volunteer opportunity is not well addressed by any of the 4 current event types.  I can have volunteers log their own hours with service project, but I still have to manually track the hours they plan to attend by following up with emails and tracking their schedules in excel. I would love to be able to manage all of my volunteer events exclusively with CERVIS.