Hello Steve,
You should be able to access the $scope in the save event depending on how your code is structured. However, you should be able to show custom validation without need to access the scope. Here is a modified version of the custom popup sample which demonstrates a possible implementation. Beside the custom rule you should note the added message placeholder and name attribute of the validated element.
Regards,Rosen
Telerik
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI now!