//Update the instructions depending on the book
function changeBook(el) {
	//Get selected value
	var currentBook=el.up('td').down('input:checked[type="radio"]').getValue();
	var books=['million','horseman'];
	for(var i=0; i<books.length; i++) {
		$$('.'+books[i]+'-only').each(function(el) {
		  el.style.display=(currentBook==books[i]) ? '' : 'none' ;
		});
	}
}

Event.observe(window, 'load', function() {
  $$('.book-selection').each(function(el) {
	  el.observe('click', function(evnt) { changeBook(evnt.element()); } );
	});
});