求高手解答VC++添加弹出菜单未定义标识符的问题

下面是一段添加弹出菜单的代码，写完时，提示说 IDR_MYPOP_MENU是未定义的标识符，求高手解答
void CMyNotepadView::OnRButtonUp(UINT nFlags , CPoint point)
{
    CMenu menu;
    menu.LoadMenu(IDR_MYPOP_MENU);
    CMenu*pMenu=menu.GetSubMenu(0);
    ClientToScreen(&point);
    pMenu->TrackPopupMenu(TPM_LEFTALIGN,point.x,point.y,this);

    //OnContextMenu(this, point);
    CView::OnRButtonUp(nFlags,point);
}