This post explains how to make a ribbon tab in Visio 2010 ribbon document-specific. Means, activate a custom ribbon tab only for a specific document.
This article discusses the implementation of a document-specific tab in a COM add-in; also, it focuses on details you might be interested in if you e.g. program unmanaged C++. Note that you could create a custom document-specific ribbon by other means, e.g. by embedding your custom interface in a document template using new Visio 2010 property Document.CustomUI
Nevertheless, one of the ways to it is