How to personalize Customer page to fix Country as a special one.

Dear experts,

Could you pleas share your knowledge on how to fix the Country to Japan and forbid it being changed when create a customer using Personalize function.

Navigation of Country item:

(R)Receivables

(N)Customer -> Customer

(A) Create    Account Site Address section

When create a customer, on the section of Account Site Address, Country is changeable to select different countries.

While customer would like to have it fix on Japan, even open the LOV you can not select other country .

I have no experience on Personalize, any advice is being great appreciated.

Best regards,

Mindy