An alternative method I used instead that was pretty painless
http://drupal.org/project/uc_custom_price
and in the custom price window for that product add the following code
$licenses = $item->data['attributes'][3];
if (intval($licenses)){
$item->price = $item->price*intval($licenses);
#drupal_set_message("Number of licenses is incorrect, must be anumber ($licenses)","status");
}else{
drupal_set_message("Number of licenses is incorrect, must be a number ($licenses)","error");
}
#print_r($item);you may need to put a print_r($item) in the code to see what your $item object looks like
Hope this helps someone