Event Execution in OWA 2007 for Menu Item Entries   

Can somebody explain what event gets executed when we click the Menu Item
"Custom Item"; part of the xml defined in the UIExtensions.xml

 
<NewItemMenuEntries>
    <NewItemMenuEntry 
            ItemType="IPM.MyCustomClass" 
            icon="MyCustomClassNewIcon.gif">
        <string language="en-us" text="Custom Item"/>
    </NewItemMenuEntry>
</NewItemMenuEntries>

date: Tue, 15 Apr 2008 02:46:03 -0700   author:   Benn Solomon