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>