which data from list?

Hi
I am trying to display a list of items from database, and would like the know how can I find out which item from the list the user has chosen to change?

This is my unsuccessful attempt which doesn't work

When a user clicks the done button, I would liek to send the itemId and the new entered quantity to a javascript, but can not figure out how to select the chnaged item
Any help will be most welcome.
here is part of the code:


<?php


while($row = mysql_fetch_array($result))
{
// Increment the total cost of all items

$totalCost += ($row["qty"] * $row["price_each1"]);
?>
<tr>
<td width="7%" height="25">
<font face="verdana" color="black" align="center">



<input size="7" name="<?php echo $row["itemId"];?>" type="number" value="<?php echo $row["qty"];?>" onClick="UpdateQty(<?php


echo $row["itemId"];?>, <?php echo $new_qty ;?>)">




</font>
</td>


<td>


<input name="check" type="submit" value ="Done" >
etc.etc.

........
function UpdateQty(a,b)
{
itemId=a;
newQty=b;
document.location.href = 'cartnew.php?action=update_item&id='+itemId+'&qty='+newQty;
}