To achieve this you can cancel creation of the filter options on ItemCreated event and build items you desire. Refer to this forum thread
which elaborates on similar subject.
All the best,
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