MsgFilter & CRichEditCtrl

Okay, I'm making a program that uses the numpad keys as macros like keys. When you hit one of the numpad keys it will put certain text in the CRichEditCtrl. Now, I've mapped message filters through the dialog editor (through right clicking the control and going to events) but what I need to know is this. How do I stop the keydown or keyup event from putting the key related text in the control?

What I have is the function OnMsgfilterEditWindow() where I have a switch on the pMsgFilter->wParam. Now when I recieve a keydown event fot the + key I want to ignore the + key event and put my own text in the control. If you know how to do this or need more info I'd greatly appreciate it. Thanks...

- Mike