function calculate()
{  
	var investment = document.getElementById("investment").value;
	if ( investment.length == 0 )
	{
		 alert("Please enter the amount of your investment");
		 return;
	}
	investment = fixNumber(investment);
	investment = parseFloat(investment);
	if ( isNaN(investment) )
	{
		 alert("Please enter the amount of your investment as a number");
		 return;
	}
	if ( investment < 0 )
	{
		 alert("Please enter an investment amount >= 0");
		 return;
	}
	
	var rate = document.getElementById("rate").value;
	if ( rate.length == 0 )
	{
		 alert("Please enter an interest rate");
		 return;
	}
	rate = fixNumber(rate);
	rate = parseFloat(rate);
	if ( isNaN(rate) )
	{
		 alert("Please enter the interest rate as a number");
		 return;
	}
	if ( rate < -100 )
	{
		alert("Please enter a rate of interest >= -100" );
	}


	var years = document.getElementById("years").value;
	if ( years.length == 0 )
	{
		 alert("Please enter the # of years you will invest your money for");
		 return;
	}
	years = fixNumber(years);
	years= parseFloat(years);
	if ( isNaN(years) )
	{
		 alert("Please enter the # of years as a number");
		 return;
	}
	if ( years <= 0 )
	{
		 alert("Please enter a number of years > 0");
		 return;
	}

	var result = investment * Math.pow(1 + (rate / 100), years ); 
	 
	var x = document.getElementById("results");

	var results = "After " + years + " years at " + rate + "% interest, your original investment of " + formatDollars(investment) + " will be worth about <b>" + formatDollars(result) + "</b>.";
	x.innerHTML = results;
	x.style.display = "block";
}