Automatic determination of condition group

Hi

My client has the following requirement:

- For 3rd party items, in few situations we might have to supply the items immediately.

- In such situations we request our supplier to supply the item directly to the customer (instead of bringing the item into our plant and then shipping)

- In the existing sales orders we change the item category of the item from ZTAN to ZTAS (3rd party item).

Customer wants to have automatic determination of the condition group 2 field at the item level (to some specified CG2 values) whenever we have the change in the item category.

Let me know how we can do this.

Regards

Jagadish