Currently, you can only set a PageBreak of a group to a preset value (e.g. 'After', 'Before', etc). For that reason, we added a Feature Request
and voted for it on your behalf to increase its priority. In future versions of our product, we consider for implementation the most demanded features, so if it has more votes, we'll move it up in our implementation list. I'm afraid until then the requirement cannot be achieved directly and we cannot offer a workaround.
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 Feedback Portal
and vote to affect the priority of the items