I have a cascading menu with templated items, where the template consists of 2 halves, left and right. I only want the child items menu to popup when the mouse if moved into the right half, not the left. Is this possible?
I am not exactly sure about your scenario. The RadMenu provides a rich set of client side APIs which allows you to interact with the Menu. In order to achieve your scenario, better approach is client side. you can check for the clicked item and cancel the ItemClick based on the MenuItem value.
Take look at the following documentaion for more on client side API. Client-Side Basics