If you are trying to add a RadPanelBar as a child control in RadGridView you will get errors. Basically, TPF (Telerik Presentation Foundation), the framework that is responsible for rendering the contents of controls like RadGridView, will throw an illegal operation exception.
To implement a similar layout I would suggest using Windows Forms panel: Dock the RadGridView to the top inside of the panel, then add the RadPanelBar as a second control in the panel, and dock it to top again. The layout should look like the one required for your application.
the Telerik team