Hi Priyanka,
You have to have some field at the CA level,. which would distinguish the different types of customers.
Account determination at CA level would have been the best solution.
However, since you are using the AD ID for a different purpose, you have to find some other field to map the segregation.
What about the Invoicing category field (FKKVKP-INV_CATEGORY)?
It is a key that references the contract account reference in invoicing.
Together with the invoicing type and invoicing process, it controls the invoicing functions.
This field is a maintainable field ,which you can maintain through SM30 against table TFK2604.
Hope it helps...
Thanks,
Amlan