Verify email address is a paypal user on wordpress website

I'm wanting someone to develop a function which checks if an email address is attached to a Paypal account on an auction website. If the email address is a valid Paypal account, the email address needs to be recorded onto that users account. Similar to what is requested here: [login to view URL] This function needs to be called when a user selects paypal as the payment method of their auction. If they select paypal, the function is called and determines whether they have recorded their paypal details for payment. If they have, nothing happens and the user is able to complete listing their auction. If they haven't, the function will ask them to supply their email address. This email address is then verified and saved onto the user profile. Regards, Simon