Clients orders queue

[S@nya]

Hello! Tell me please the next: how can i make the order queue for clients orders in the time? In other words, i have a Prastashop webstore which provides some services, when customer placing the order to some product or service he must to get some place in the queue after the clients, who has older orders and see the message like this: "Your order is in line with number 123, order will be processed within 5-7 days..."

 

Sorry for bad English, waiting for reply.