I can suggest using databinding to do this. The IsChecked and IsEnabled properties of the CheckBoxes can be databound. Then, another property in your ViewModel may track whether there are any checked items.
You can have a look at the attached project.
the Telerik team
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items.