Have a look through the ButtonFacade support of other addons for examples. Here - these are separate plugins that add BF support, that should be easy enough to follow.
http://www.wowinterface.com/download..._ItemRack.html
http://www.wowinterface.com/download...tonFacade.html
http://www.wowinterface.com/download...tonFacade.html
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"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff,
The Tao of Pooh