Untitled

<html>
<head>
<script type="text/javascript">
function performCalc()
{
	var firstBox = parseInt(document.getElementById("num1").value);
	var secondBox = parseInt(document.getElementById("num2").value);
	var calcResult = firstBox + secondBox;

	document.average.result.value = calcResult;
}
</script>
</head>

<body>
<form method="post" action="" name="average">
<p>
First number:
<br>
<input type="text" id="num1" name="num1" value="5"/>
</p>

<p>
Second number:
<br>
<input type="text" id="num2" name="num2" value="4"/>
</p>

Final Result:
<br>
<input type="text" id="result" name="result"/>
</p>

<input type="button" value="Click me!" onclick="performCalc()" />
</form>
</body>
</html>