title: Accessing an existing control on Outlook ribbon
body: <p>I want to add a CommandBarButton to an existing CommandBarPopup that displays in an Outlook MailItem compose ribbon.  (Ribbon ID: Microsoft.Outlook.Mail.Compose)</p>
  
  <p>I found code that shows me how to add a new CommandBarButton to a CommandBarPopup, but I can't find out how to get a reference to the CommandBarPopup. This is an existing Popup on the ribbon, not a custom popup. </p>