Just getting into 3.0 and setting up our PayPal account for use in 3 different stores (NopCommerce)

Looking for assistance in creating the proper IPN "call" for use with each different store, sent to PayPal - So Paypal will route the IPN back to the correct NopCommerce handler page.

Can this be done easily, without me having to rebuild my site code?
(for example: edit a file or two via ftp, in the site(s))

Thanks for your help!

If it takes more detail or information PM me.

FLETCH