PlugIn for MS-Office through C#

Question

Hi all, Well This is my first post here. I am developing an application in C#. (Visual Studio.Net 2003) Where I want to develop a Plug-In for MS-Office (typically Word,Excel & PowerPoint). The functionality of this Plug-In will be like this. - A button with The application logo will be displayed in Office toolbar. - When User click on this button the current file will be saved and the file is available my application for further processing. Can Anybody please guide me what are the steps to develop such a kind of plug in. Thanks & Regards Harry