Custom Invoive Module

Our current e-Commerce system is using opencart.
We are looking for custom module Software CD-Key.

After customer purchased the software, they can immediate get the key from the invoice number.
admin must be able to insert the license serial number into data base from administrative back end of open cart.

Does any know know the module similar to it either free or paid version please update me

I haven't read the full details of this module but it may interest you
http://www.opencart.com/index.php?route ... on_id=1914