Hmm, that's not the best title - but maybe a contrived code sample or two will help out in explaining why sometimes I weep when I look at certain bits of code.

Imagine if you would, creating a context menu with a few dynamic elements without IDs

menu->append("Hello");
menu->append("This");
menu->append("is a");
menu->append("Test");

And you responded to the elements not by an ID number, but by a position index.

switch(selectedIndex):
{
    case 0: doHello(); break;
    case 1: doThis();  break;
    case 2: doIsA();   break;
    case 3: doTest();  break;
}

And then when you look at the code that creates the menu item with greater scrutiny, you notice it's not as simple as you once thought...

menu->append("Hello");
if(hasPermission(SECURITY_RIGHTS_THIS))
    menu->append("This");
menu->append("is a");
menu->append("Test");

That's why I wept.
If an unlucky user doesn't have SECURITY_RIGHTS_THIS all the following menu items will be off by one!
This isn't a hard coded COM interface contract, but it IS a handshake usage contract that a future maintenance programmer (such as myself) may not even be aware of!

So here's a simple solution (if you can't change it to use proper IDs because it would effect to many systems):
Keep a table of what menu items were added and their appended menu index. Maybe something along the lines of

enum PossibleMenuItems { pmiHello, pmiThis, pmiIsA, pmiTest, pmi_MAX };
typedef map<int, PossibleMenuItems> IndexToMenuItem;
IndexToMenuItem m_IndexToCommand;
...
int nMenuIndex = 0;
// For each item you add, append it AND record it...
menu->append("Hello");
m_IndexToCommand[nMenuIndex++] = pmiHello;

if(hasPermission(SECURITY_RIGHTS_THIS))
{
    menu->append("This");
    m_IndexToCommand[nMenuIndex++] = pmiThis;
}
...

Then in the menu handler...

IndexToMenuItem::iterator itFind = m_IndexToCommand.find(selectedIndex);
if( itFind != m_IndexToCommand.end() )
{
  switch( (*itFind) )
  {
    case pmiHello: doHello(); break;
    case pmiThis:  doThis();  break;
    case pmiIsA:   doIsA();   break;
    case pmiTest:  doTest();  break;
  }
}

Now it no longer matters if an item is not added to the menu. As long as the table is updated - I'm happy.