The m_pWndMenu member variable holds a pointer to the command-processing window. This is useful if you want to show TAH context menus on controls placed in dialogs. In these situations you cannot use AfxGetMainWnd() because your menu commands might be either grayed, or worse, handled by another (hidden) window. So, m_pWndMenu will have the containing CDialog pointer.
这是codeproject上面对这个参数的解释,可惜小弟英文不行,没看懂.望各位大哥给予解释说明.