Similar to the RadComboBox' OnClientFocus event - http://www.telerik.com/help/aspnet-ajax/combobox-onclientfocus.html
Duplicated with http://feedback.telerik.com/Project/108/Feedback/Details/170815-add-a-couple-of-events-to-the-radeditor-1-when-the-control-gets-focus-2-whe