function calculateBodyFatPercentage(btn) {
	var elGender = document.forms["bodyfat"].elements["gender"];
	var elWeight = YAHOO.util.Dom.get("weight");
	var elWaist = YAHOO.util.Dom.get("waist");
	var o = YAHOO.util.Dom.get("bodyfatvalue");
	if(!btn.id){
		if(isNaN(parseFloat(elWeight.value))){
			resetBodyFatPercentage(o);
			return;
		};
		if(isNaN(parseFloat(elWaist.value))){
			resetBodyFatPercentage(o);
			return;
		};
	};
	if(isNaN(parseFloat(elWeight.value)) || elWeight.value<=0){
		resetBodyFatPercentage(o);
		return warnInvalid(elWeight,"Please enter a positive number for your weight in pounds.");
	};
	if(isNaN(parseFloat(elWaist.value)) || elWaist.value<=0){
		resetBodyFatPercentage(o);
		return warnInvalid(elWaist,"Please enter a positive number for your waist in inches.");
	};
	var BF;
	if(elGender[0].checked) {
		BF = -76.76;
	}else {
		BF = -98.42;
	};
	BF += (4.15*elWaist.value - .082*elWeight.value);
	if(BF>0){
		o.innerHTML = Math.round(BF/elWeight.value*100) + "" + "%";
		return;
	}else{
		resetBodyFatPercentage(o);
		if(btn.id){
			return warnInvalid("","Either the weight entered is too low or the waist size entered is too low.");
		};
	};
	resetBodyFatPercentage(o);
};

function resetBodyFatPercentage(obj){
		obj.innerHTML = "&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;";
};

YAHOO.util.Event.addListener(document.forms["bodyfat"].elements["gender"],"click",calculateBodyFatPercentage);
YAHOO.util.Event.addListener(YAHOO.util.Dom.get("weight"),"keyup",calculateBodyFatPercentage);
YAHOO.util.Event.addListener(YAHOO.util.Dom.get("waist"),"keyup",calculateBodyFatPercentage);