MouseWheel (Main Control) example for C++ 4.0 and later

void CMyClass::OnMouseWheel(short nDelta, short Shift, long x, long y) 
{
   if (Shift ==2) //CONTROL Key is Pressed
   {
         if(nDelta < 0)
         {
            if (m_Lead1.GetPaintZoomFactor() < 100 * 16)
            {
               m_Lead1.SetPaintZoomFactor(m_Lead1.GetPaintZoomFactor() * 2);
            }
         }
         else
         {
            if (m_Lead1.GetPaintZoomFactor() > 100 / 16)
               m_Lead1.SetPaintZoomFactor( m_Lead1.GetPaintZoomFactor() / 2);
         }
   } 
   else
   {
      m_Lead1.GetVScrollInfo().SetPos(m_Lead1.GetVScrollInfo().GetPos() - nDelta);
   }
}

void CMyClass::OnLoad() 
{
   m_Lead1.Load ("c:\\1.bmp",0,0,1);
   m_Lead1.SetEnableMouseWheel(TRUE);
}