<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script>$(document).ready(function(){
$(".sumtotal").each(function() {
$(this).keyup(function(){
calculateSum();
});
});
});
function calculateSum() {
var sum = 0;
$(".sumtotal").each(function() {
if(!isNaN(this.value) && this.value.length!=0) {
sum += parseFloat(this.value);
}
});
$("#item2_number_1").val(sum.toFixed(2));
}</script>