function check_quantity(iItemId)
{
    if (ready_to_accept())
    {
        xmlHttp.open('GET', 'ajax_commands/check_quantity.php?id=' + iItemId + '&quantity=' + document.getElementById('quantity_' + iItemId).value);
        xmlHttp.onreadystatechange = function myFunction()
        {
            if (ready_to_process())
            {
                if (xmlHttp.responseText != 'correct')
                {
                    aInformation = xmlHttp.responseText.split('|');
                    alert('I am sorry, but there is only ' + aInformation[1] + ' items left for ' + aInformation[0] + '. Your order quantity will be updated accordingly.');
                    document.getElementById('quantity_' + iItemId).value = aInformation[1];
                }
            }
        }
        xmlHttp.send(null);
    }
    else
    {
        setTimeout('check_quantity(' + iItemId + ')', 250);
    }
}