C / C++ / MFC

BOOL CMyFrameWnd::PreTranslateMessage( MSG *pMsg )
{
   BOOL bMessageHandled = FALSE;

   switch( pMsg->message )
   {
      case WM_LBUTTONDOWN:
      {
        if( ::GetFocus == MyEditWnd )
        {
          if( !IsContentOfMyEditWndOK )
          {
            ShowMessageBox( "You cannot change value");
            //ShowMessageBox has got DoModal inside, which pumps messages.
           //Unfortunately it causes my *pMsg parameter to be changed.
          }
        }
        break;
      }
   }
  if( !bMessageHandled )
  {
     bMessageHandled = CFrameWnd::PreTranslateMessage( pMsg ); //I get assertion has failed here, because I am sending pMsg->Hwnd changed with 'ShowMessageBox'
  }

  return bMessageHandled; //I want to show messagebox and let WM_LBUTTONDOWN to be processed, because I do not want to trap focus in my Edit. So I am returning FALSE here. But it has no sence since the pMsg has changed. It is no longer WM_LBUTTONDOWN. 
}

BOOL CMyFrameWnd::PreTranslateMessage( MSG *pMsg )
{
   BOOL bMessageHandled = FALSE;
   MSG oRememberMsg;

   switch( pMsg->message )
   {
      case WM_LBUTTONDOWN:
      {
        if( ::GetFocus == MyEditWnd )
        {
          if( !IsContentOfMyEditWndOK )
          {
            oRememberMsg = *pMsg; 
            ShowMessageBox( "You cannot change value");
            *pMsg = oRememberMsg; //now pMsg is WM_LBUTTONDOWN again 
          }
        }
        break;
      }
   }
  if( !bMessageHandled )
  {
     bMessageHandled = CFrameWnd::PreTranslateMessage( pMsg ); //I am not getting assertion has failed, because pMsg->HWnd is correct now (the same as at the beginning)
  }

  return bMessageHandled; //Now I am forwarding my catch WM_LBUTTONDOWN and my Edit loses focus
}