Operator 'cart-details' is called for rendering the payment details form.

@param $op
@param $arg1
  current order

  form with the specific payment details

Here the total card value is tested and a date form is added when applicable.

case 'cart-details':
$details = variable_get('uc_cod_policy', t('Full payment is expected upon delivery or prior to pick-up.'));
  if ((
$max = variable_get('uc_cod_max_order', 0)) > 0 && is_numeric($max)) {
$details .= '<p>'. t('Orders totalling more than !number are <b>not eligible</b> for COD.', array('!number' => uc_currency_format($max))) .'</p>';
  if (
variable_get('uc_cod_delivery_date', FALSE)) {
$details .= uc_strip_form(drupal_get_form('uc_payment_method_cod_form', $arg1));