Modalviews have to be defined on the page at startup. It would be helpful if a modalview (and a view) could be returned or replaced as a MVC partial view, i.e. make it possible to create and open a modalview after the page has loaded. 
See also: http://www.telerik.com/forums/dynamically-create-a-modalview#1f2q7wMEu02yYX1_6El2hg