## Live javascript calculating

Hi there!

I hope one of you javascript experts can help me out on this one. In html and PHP I made a purchase script. Al the products are listed inside a WHILE loop. The problem is, when I POST it starts entering data in the database. I would like the possibility that when I enter a number in the "aantal" field that it instantly calculates live how much it is going to cost.

So, "aantal\$i" * inkoop_prijs = Subtotal
And, all Subtotals together = Total

Big respect to the one that solves this

Code:
```	<?php
if(isset(\$leverancier_id)) {
\$i = 1;
\$totaal = 0;

while(\$prodinfo = mysql_fetch_assoc(\$prodres)) {  ?>
<tr>
<td><?=\$prodinfo['product_id'];?></td>
<td><?=\$prodinfo['naam'];?></td>
<td align="center"><input name="aantal<?=\$i;?>" type="text" value="<?=\$_POST['aantal'.\$i];?>" size="5" /></td>
<td><?=number_format(\$prodinfo['inkoop_prijs'], 2);?></td>
<td align="right">
<input type="hidden" name="product_id<?=\$i;?>" value="<?=\$prodinfo['product_id'];?>" />
<input type="hidden" name="inkoop_prijs<?=\$i;?>" value="<?=\$prodinfo['inkoop_prijs'];?>" />Subtotal</td>
</tr>
<?php
\$i++;
} }
?>

<tr>
<td colspan="2" valign="top" align="right"><strong>Total:</strong></td>
<td colspan="2" valign="top">incl. 19&#37; BTW </td>
<td align="right"><strong>&euro; </strong></td>
</tr>```