Using callback function

jQuery Code:

	$(function(){
		$(".tabs-trigger").switchable(".tabs-panel > p", function(event, index) {
        	var obj = $("#checkbox");
			if ( index > 0 && !obj.is(":checked") ) {
				obj.parent().addClass("error");
				return false;
			}
			obj.parent().removeClass("error");
		});
	});
	

HTML Code:

	<div class="tabs-trigger">
		<a href="#">First</a>
		<a href="#">Second</a>
		<a href="#">Third</a>
	</div>
	<div class="tabs-panel">
		<p><input type="checkbox" id="checkbox" /> I accept these terms and conditions</p>
		<p>Tab Panel 2</p>
		<p>Tab Panel 3</p>
	</div>