The RadDock control could help you achieve the desired functionality. Please check its online demos
for more information and examples with the RadDock.
RadDock is part of the RadControls for ASP.NET AJAX suite and you can find information about its cost in the Telerik's online store
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed