Once an order is placed, I programmatically generate associated shipments (because of different manufacturing time on my products)

I can then have for a single order several associated shipments:
ex:
- Shipment #100000110 in 2 days for items 1 and 2
- Shipment #100000111 in 5 days for item 3

I would like to access the shipment number associated to specific item :

something like :

	$order = Mage::getModel('sales/order')->load($_order_id);
	$_items = $order->getAllItems();

	foreach ($_items as $_item)
	{
		$ciid = $_item->getId();
		$shipmentNbr = $_item->getShipment()->getIncrementId();
		...
	}


Thank your for your help,