Add a form and populate the total box

<style>
#totaltop{position: fixed; top:20px; right: 20px;}
</style>

<script type="text/javascript">
var i=0;
var t=0;
var x=0;
var values = new Array();
  values[0]=0;
  values[1]=0;
  values[2]=0;
function sum(el){
  x=document.getElementById(el).value;
  x=x*1;
  values[el.substr(1)]=x;
  for (i in values){
    t+=values[i];}
  document.getElementById('total').value=t;
  document.getElementById('totaltop').value=t;
  t=0;}
</script>

<form name="form">
<input id="a0" onkeyup="sum(id);" /><br />
<input id="a1" onkeyup="sum(id);" /><br />
<input id="a2" onkeyup="sum(id);" /><br />
<input id="total" readonly="readonly" /><br />
<input id="totaltop" readonly="readonly" /><br />
</form>