Changing WPFToolKit Calendar control

Question

Hi,

Im looking to add a new feature to the WPF Calendar control,

At the moment this control allows you to set blackout dates... So you can add a group of dates in which cannot be selected and they are shown grayed out

I want to add another collection of dates in which I can highlight in red to denote some kind of special events that happen on those dates.

Just looking at the code in the WPFToolKit it seems as though they have not made the control to amenable to changes....Like the CaledarItem class is sealed...

Any clues as to how I can go about adding this functionailty?

Thanks