Hello Rakesh,
There are two requirements here.
1. Update of Upcountry / Local customer in Customer Classification which is a standard setting to be done here - IMG - Sales and Distribution - Master Data - Business Partners - Customers - Marketing - Define Customer Classifications.
Subsequently you need to maintain the Customer Classifications in Customer master data records. For new customers created in future, to ensure this field is filled, you can mark it as required.
2. Update of ZAISUBLOC - Since this is a Z-program developed specifically for your company, I guess none of us here would be able to help you. You will have to work your technical team (ABAPers) to make the understand the current logic of the program & suggest necessary changes.
Thanks,
Jignesh Mehta