怎样去掉子窗口(childframe)的凸起的边框

void CRightFrame::OnWindowPosChanging(WINDOWPOS* lpwndpos)
{
    lpwndpos->x -=2;
    lpwndpos->y -=2;
    lpwndpos->cx +=4;
    lpwndpos->cy +=4;
    CFrameWnd::OnWindowPosChanging(lpwndpos);
}

void CRightFrame::OnWindowPosChanged(WINDOWPOS* lpwndpos)
{
    lpwndpos->x -=2;
    lpwndpos->y -=2;
    lpwndpos->cx +=4;
    lpwndpos->cy +=4;
    CFrameWnd::OnWindowPosChanged(lpwndpos);
}