Friday 11 June 2010 6:50:42 am

Answering to myself :

$http = eZHTTPTool::instance();
$orderID = $http->sessionVariable( 'MyTemporaryOrderID' );
$order = eZOrder::fetch( $orderID );
$items = $order->productItems();
$count = count( $items );

This do the job.

Hope this help