<script type="text/javascript">
function startCalc(value1, value2, sum)
{
interval = setInterval("calc('" + value1 + "', '"+ value2 +"', '"+ sum +"')", 1);
}
function calc(value1, value2, sum)
{
var one = document.getElementById(value1).value;
var two = document.getElementById(value2).value;
document.getElementById(sum).value = (one) - ((one) * (two)) / 100;
}
function stopCalc()
{
clearInterval(interval);
}
</script>
<script type="text/javascript">
function aggiorna()
{
document.getElementById('campo2').value = document.getElementById('campo1').value;
document.getElementById('campo3').value = document.getElementById('campo1').value;
}
</script>
<form name="autoSumForm">
<?php
$num=20;
<input type="text" id="campo1" onchange="aggiorna()" />
//il campo 2 dovrebbe essere id=\"prezzo$k\"
for($k=1;$k<=$num;$k++)
{
echo"
<input type=\"text\" id=\"prezzo$k\" name=\"prezzo[]\" onfocus=\"startCalc('prezzo$k', 'sconto$k', 'prezzofin$k')\" onblur=\"stopCalc();\" />
<input type=\"text\" id=\"sconto$k\" name=\"sconto[]\" onfocus=\"startCalc('prezzo$k', 'sconto$k', 'prezzofin$k');\" onblur=\"stopCalc()\" value=\"10\" readonly=\"readonly\" />
<input type=\"text\" id=\"prezzofin$k\" name=\"prezzofin[]\" readonly=\"readonly\" />
<br />";
}?>
</form>