Business Process stage onChange event

You can’t cancel the stage change using code in a handler for this event

//Put the below code in the onload function of the form

Xrm.Page.data.process.addOnStageChange(onStageChange); 

function onStageChange(ExecutionContextObj)

{
debugger;
alert(ExecutionContextObj.getEventArgs().getDirection()) // alerts "next" or "previous"
} 

This onStageChange method gets trigger when you click next or previous button. But it is not triggered when you click the link of the stage.