$(document).ready(function() {
	$("input[@name=addition]").focus( function()
	{
		startCalc();
	});
	$("input[@name=addition]").blur( function()
	{
		stopCalc();
	});
});

function startCalc(){
  interval = setInterval("calc()",500);
}
function calc(){
	var fieldSum = document.getElementsByName("addition")
	var runningTotal = 0
	for (var i=0; i<fieldSum.length; i++)
	{
		var runningTotal = (runningTotal * 1) + (fieldSum[i].value * 1);
	}
	document.getElementById("boxsum").value = runningTotal;
}
function stopCalc(){
  	clearInterval(interval);
}