Activating a Custom Tab on the Ribbon When a Document Is Opened

Harry 'Play It Again Sam' Miller has posted a wonderfully funny video on this topic - with a serious message. You've got to check this one out: https://blogs.msdn.com/vsto/archive/2008/08/12/activating-a-custom-tab-on-the-ribbon-when-a-document-is-opened.aspx.