How can I complete the picking from XML-RPC (Deliver Products / "Deliver" button from web ui)?

my code looks like this now (nothing happens):

     $this->msg = new xmlrpcmsg('exec_workflow');
     $this->msg->addParam(new xmlrpcval($this->database, "string"));
     $this->msg->addParam(new xmlrpcval(1, "int"));
     $this->msg->addParam(new xmlrpcval($this->password, "string"));
     $this->msg->addParam(new xmlrpcval("stock.picking.out","string"));
     $this->msg->addParam(new xmlrpcval("button_done", "string"));
     $this->msg->addParam(new xmlrpcval($order_id, "int"));
     $this->res = &$this->client->send($this->msg);
     $order[] = $this->res->value()->scalarval();