How to get SetFocus events with Radio Buttons in MFC

Working in MFC today I wanted to know when the user clicked on a radio button so I could change the default button with SetDefID(IDC_LOAD_MEMORY_BTN) but for some reason after adding the event handler for BN_SETFOCUS I never got a notification.  After poking around the radio button’s properties in Visual Studio 2008 I found Notify – changing it from False to True allowed me to start receiving focus events