Angular UI- tour next event

I am using angular-ui-tour [] to display overlays in my web app. I have setup an event listener when the steps are changed

tour.on('stepChanged', function (data) {
                    //do something 

This listener gets executed when I click next or previous on my overlay. But i want the listener code to be executed on next button click only. I could not find any events specific to next button click. Please suggest if there is any.