There is a 1.4% of the transaction total + 20 pence charge added to each order

Preview your form and find the div id of the elements you want to work with and make a note of them.

For me my id's were item1_number_1 and item2_number_1. Your may be different.

To use this script add a html element to your form and paste this into it. Adjust the id's to match yours.

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> <script type="text/javascript">$(document).ready(function(){
$('#item1_number_1').keyup(function(){
var valone = $('#item1_number_1').val();
var valtwo = .20;
var valthree = 1.014;
var total = ((valone * valthree) + (valtwo));
$('#item2_number_1').val(total.toFixed(2));
});
});</script>

To have the total inaccessible to the users open the myformname.html after you do the manual export and add readonly to the elements html code.

<input name="total" id="item2_number_1" type="number" min="0" max="999999999"
step=".01" autocomplete="off" data-hint="" readonly />