Small query

Hello,
o my signup page, i have two fields - country and phone number. right now, user chooses the country via a drop down option and in phone number he has to write the country code. I want some arrangement by which as soon as he chooses the country, country code should be displayed automatically. I have the country codes but i don’t know how to make the script for it. can some one please guide me?

Also i want that whenever a password is changed a message should go to user’s phone. is this possible too?

Thanks
Shail