How to add new filed in Create New User Upgrade admin page


I want allow user to select two types of upgrade amount like $10 per month or $110 per year. so i need extra filed Cost
in the
user upgrade admin page. How to allow users to select month or year in the account/upgrades page. When they select subscribe button,before that need to select the length option month or year. Example users select month the amount is $10 needs to go paypal or user select year the amount $110 needs to go paypal. please any one help me.