Update Sum
Updates a value based on a selected <option>
by ChrisStanyon
HTML
<select id="values">
<option value="1">Value 1</option>
<option value="2">Value 2</option>
<option value="3">Value 3</option>
<option value="4">Value 4</option>
</select>
<label for="total">Total:</label>
<input type="text" id="total" value="0">
JavaScript
var runningTotal = 0;
$('#values').change(function() {
runningTotal += parseInt($(this).val());
$('#total').val(runningTotal);
});