Problem while overriding CChildFrame::PreTranslateMessage

In a simple MDI application, I tired to override CChildFrame::PreTranslateMessage to pre-process some events or just drop them if meet some condition. However, I found that all events were received twice out there, I don't why MDI framework dispatched same event twice to CChildFrame::PreTranslateMessage, but that was really unexpected, and how to avoid that?

Thanks.

1. Do you mean Events or Messages?
2. What kinds of Events / Messages are you going to handle in CChildFrame::PreTranslateMessage and why in CChildFrame class and why in PreTranslateMessage?
3. Did you consider to implement message handlers instead?