Most probably the event you are searching for is not LayoutUpdated, but SizeChanged. You could take a look at the following MSDN reference: http://msdn.microsoft.com/en-us/library/system.windows.frameworkelement.layoutupdated(VS.95).aspx and on the following article that explains what happens in very interesting manner: http://www.dotblogs.com.tw/kan/archive/2009/03/03/7352.aspx.
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?
Telerik Public Issue Tracking
system and vote to affect the priority of the items.