How to make an automatic pop up while creating customers which will ask the country name & according to country system will give numbers for customer ?

Hi All,

I have a requirement for my client while creating customer masters in XD01 tcode. system should give a pop up asking the country name. Then user have to enter the country in the pop up, According to the country, Numbers for customers will be assigned automatically.

Thanks & Regards,

Shaktiprasad Dash