function CalcBMI()
{
	var form = $('bmi-form');

	var feet   = parseFloat($F( form['bmi-feet'] ));
	var inches = parseFloat($F( form['bmi-inches'] ));
	var weight = parseFloat($F( form['bmi-weight'] ));

	if(feet <= 0 || isNaN(feet) || inches < 0 || isNaN(inches) || weight <= 0 || isNaN(weight))
	{
		$('bmi-result').update('Please enter positive numeric values for all fields.');
		return false;
	}

	inches += feet * 12;

	var bmi = Math.round((weight * 703.0) / (inches * inches));

	var category = "";
	if(bmi < 16.5) {
		category = "severely underweight"; }
	else if(bmi < 18.5) {
		category = "underweight"; }
	else if(bmi < 25) {
		category = "normal"; }
	else if(bmi < 30) {
		category = "overweight"; }
	else if(bmi < 35) {
		category = "obese"; }
	else if(bmi < 40) {
		category = "clinically obese"; }
	else {
		category = "morbidly obese"; }

	$('bmi-result').update('Your body mass index (BMI) is ' + bmi + '. The World Health Organization categories this BMI as ' + category + '.');

	return false;
}