Here ie deal:
I already work with the calculate example and I get an percentage value of a process but I need to define that if User make "0" on textfield "e1" I will run a formula, and if the user get some data on textfield "e! I will run anothe validation process, Here is the actual code:

<script type="text/javascript">
function calculateTextfinal()
{
var op1=document.getElementById('e1');
var op2=document.getElementById('total1');
var result =document.getElementById('total2');

if(op1.value>0){(op2.value/100)*(10000/81)
}
else
{
(p2.value/100)*(10000/66)}

result.value=0;
result.value=parseInt(result.value);

}
</script>

but is not working,

Im not have experience on Javascript so any help could be great