update of session variable using <input> tags

im having a problem with my WML ediot shopping cart code

the default value of a certain <input> tag is taken from a session array [cart] and i wish to edit such value. how can i edit the value in the input and at the same time automatically assign that new value to the session array without having to go to another card?so that as soon as the user edits the value inside the input tag it is automatically reflected in the value of the session array (in case it is possible)

here's the code in case it cud b of help

<wml>

<card id="card" title="Edit Cart">
<do type="Accept" name="Accept">
<go href="Wcart.php?save=1">
</go>
</do>

<p>
<?php
include ('db.inc');
session_start();

if ($_SESSION['cart']&&array_count_values($_SESSION['cart']))
{
echo "<em>CART CONTENTS:</em>";
foreach ($_SESSION['cart'] as $scbpid => $qty)
{
$sql = "SELECT description from scbp WHERE SCBP_id=$scbpid";
$result = mysql_query($sql);
$row = mysql_fetch_array($result);
$name = $row['description'];
echo "$name<input name='$scbpid' format='3N' value='$qty'/>";
}
}
else
echo "cart empty";
?>
</p>
</card>
</wml>

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Your help would much be appreciated