how to know which state in CCSrollLayer

I use CCscrollLayer for choose level scene in this link: https://github.com/cocos2d/cocos2d-x-extensions/tree/master/extensions/CCScrollLayer
http://www.youtube.com/watch?v=ViJoNQDWB5Q

But, how to know when scrollLayer stop, m_currentLayer is?? (

Thank u for help :((

Can i help me:(