I would recommend not to use the OpenerElementId property in such scenario - it
is intended to be used in simple scenarios only when you want to open a
RadWindow popup by clicking on some element.
In cases where there is a
more complex logic, I strongly recommend to use either the Client-Side or the
Server-Side API for opening the RadWindow.
More information on how to set
various server and client side properties is available in the documentation, section
Controls / RadWindow / Programming.
the Telerik team