[news.eclipse.platform.swt] retrieve MenuItem by ID

[Luciano Boschi <boschi@xxxxxxxxxxxxxxxxxxxxx>]

Hi everyone,
I'm developing an Eclipse plugin.
I need to enable/disable a menu item programmatically.

The question is: how can I access the MenuItem object?
for instance: from its IWorkbenchWindowActionDelegate.

The only things I know are the MenuItem id and menubarPath (as specified 
in the plugin.xml file).

Thank you, I didn't find answer searching help or snippets

Bye
Luciano