function calcDecay() {
	if (document.getElementById('RulesetBpDecay').value == '') {
		duration = parseInt(document.getElementById('RulesetQuestionDuration').value);
		interval = parseInt(document.getElementById('RulesetBpInterval').value);
		document.getElementById('RulesetBpDecay').value = ((100 / duration) * interval).toFixed(2);
	}  
}