How can serial numbers be produced during creating production orders???

Question

In our company，the basic manufacture process are as follows:
1.CO01  Create production order
2 MB1A  Goods issue to production order
3 CO11N Produciton order confirmation
4 MB1A Goods Receive
For some finished product with serial number management, when doing MB1A goods receive ,we
will input the serial numbers into the SAP for the first time.That means the serial numbers
was produced when doing MB1A.
But for some reasons,we wish when we create a production order,the serial numbers can be
produced for the finished product.That means we will release a production order,the serial
numbers can be produced for the finished product of the production order,can be auto
produced or by input manually.
We do not want the the serial numbers to input into the SAP until doing MB1A.
What can we do to produce the the serial numbers for the first time after release a
production order?
How can serial numbers be produced during creating production orders?
Thanks very much for any reply!!

Answer 1

You should configure the SN profile to allow that the order can be released w/o SN;
but... for the other issues, we have used and user exit that - after saving the order - generates a SN according to a given logic. 
We could not fina dan easy way of creating the SN after relasing the order or when doing the GI.
Regards