CEdit controls

I´m coding VC++ using the MFC. In my Project I use a class CNCEdit, which is deriven from a CEdit Control.What I want to do, is to overload some class mebers in that way, that i get a red bar in the middle of the edit window, that is comparable like the breakpoint bars in the source editor of VC++.
Of course that should be no problem, if I overload the OnPaint Message-Handler, but the mistery is, that the bar is drawn correctly, but if I enter something in the edit control, the bar is overwritten by the text i typed in.
My questions now, are:
1.) What member function must be overloaded ???
2.) What message-handlers must be rewritten ???

I have already downloaded two projects from this site. The object of them was to design a edit-control, that colourizes the text in a CEdit in a syntax-depending way. The problem here was, that the new editor was deriven from a CEditView class and not from a CEdit control, like I want to do. My View-class is deriven from a CFormView.

So please help me, if You can...

Max