Scroll window:Urgent

I derived a CWnd class named C2WinBox and override OnVScroll function With SetScrollPos, ScrollWindow, and UpdateWindow.
Then I used C2WinBox object created a Window within a CPropertyPage derived class OnInitDialog function. The Window has WS_VSCROLL style.
then I created some controls on The window such as CEdit box, CCombobox, CStatics etc.(controls
are created by code not by resource template.)
but when I Sctoll the window, the contents on the window are mess up. is there anyone know how to make the window clear when scrolling.
I appreciate any reply.