Need a small assistance for meeting a client requirement

 Hi,

i need a small requirement assistance

i have the following data in my cursor statement

order_number   header_id    line_id    item     quantity       shipping_method   delivery_number

1001 1101         2201     AS54999      5              DLF-ROAD             

1001 1101         2202     AS55999      5              DLF-ROAD             

1001 1101         2203     AS54888      5              FEDEX-ROAD             

1001 1101         2204     AS55888      5              FEDEX-ROAD

1001 1101         2205     ASD6888      5              FEDEX-AIR

1001 1101         2206     ADD6888      5              DLF-AIR

Now i need to create a delivery-number  for each shiment method

In the above data  there is four different shipment methods so that i need to create four deliveriy number

and delivery number is a sequence

but i am facing the difficulty for creating the delivery number for each shipment method

any help in this appreciated

excepeted out put is