auto switch price and store based on customer address during checkout

i have Magento installed with 2 store

1: India Store and us store
2: i have set the price of product A in India store as 100 INR and 120 INR in Us Store
3: now what i want, if user is doing checkout from Indian store and in checkout he select country other than india then checkout total should be based on us store

basically i want to auto switch store based , final checkout amount bassed on customer country in checkout

i am not able to get logic for same please help me with it