Superponer NSView con WebView

I am trying to put an NSView onto of a WebView so that I can get when the mouse is scrolled. You cannot subclass WebView and get the scroll events because they are sent to a private view. Is there any way that I can put an NSView onto of the WebView to just get when a scroll event occurs without interfering with the way the WebView receives its actions. Right now I just have an NSView onto of a WebView in Interface Builder. When I scroll, I get the event from the NSView, but the WebView no longer will scroll. Is there some sort of way to trigger two events respective with the views while stacked on top of each other?

¡Gracias!