function initRothCalc(){
	// form validation
	var years = document.getElementById('years_of_withdrawals');
	var select_obj = document.getElementById('retirement_rate_of_return');
	var objFrm = document.getElementById('roth-form');
	var objHidInput = document.createElement('input');
	objHidInput.type = 'hidden';
	objHidInput.name = 'retirement_rate_of_return';
	objHidInput.id = 'retirement_rate_of_return';
	objHidInput.value = '1';
	years.onblur = function() {
		var blnPrev = select_obj.disabled;
		select_obj.disabled = (this.value <= 1) ? true : false;
		if (select_obj.disabled) {
			objFrm.appendChild(objHidInput);
		} else if (blnPrev){
			objFrm.removeChild(objHidInput);
		}
	}
	document.forms[0].retirement_rate_of_return[0].disabled = (years.value == 1) ? true: false;

	// set form event handler
	var closeForm = document.forms[1];
	closeForm.onsubmit = function(){history.back();return false;};
	closeForm.getElementsByTagName('input')[0].onclick = function(){self.close();return false;};
}
addEvent(document,"readystatechange",initRothCalc);