在扩展CFileDialog时捕获ON_CBN_SELCHANGE和其他下拉事件

I am trying to create a custom file save dialog for XP using C++/VS2008. My dialog will have three dropdowns and an edit box. I need the contents of the dropdowns to dynamically update when selections are made on other dropdowns. Hence, my need to catch the CBN_ events.I am trying to create a custom file save dialog