The idea is not new, to say the least, the interested ones may check this topic at codeguru.com. This sample demonstrate a most simple (and straightforward) method how to do the task and is basically a demo for a simple custom control, which is based on existing control.
Keywords: CEdit, ES_MULTILINE, WS_HSCROLL, WS_VSCROLL, ShowScrollBar, DECLARE_WND_SUPERCLASS, SubclassWindow
Visual C++.NET 2005 source code can be downloaded here, compiled binary – here.