var el = YAHOO.util.Dom.get('terms'); 
var field = new YAHOO.inputEx.CheckBox({parentEl: el, sentValues:[true, false], rightLabel:"You must agree to the terms and conditions", value:false}); 
field.updatedEvt.subscribe(function() { 
	if (field.getValue()) {
		if (oButton.get('disabled')) {
			oButton.set('disabled', false);
		}
	} else {
		oButton.set('disabled', true);
	}
}); 

var onButtonClick = function (e) { 
   //return false;
   //alert(e.target); 
}; 

var oButton = new YAHOO.widget.Button("submitbutton", { label: "Submit", onclick: { fn: onButtonClick } });