Using paypal and MySQL for a paid token system.

I have a database that holds a members current token balance. What I want is the ability of a member to be able to buy tokens to increase their token balance.

Each token will cost $1.00. Members can choose how many tokens they wish to buy, and this amount (in $) will be sent to my Paypal account.

Upon successful completion of the transaction the members account is updated to show the new number of tokens.

I already have a paypal integration for the e-commerce store within my website. This feels like it should be easy to accomplish - I just simply do not have the time.