Affiliates plugin, but not for existing users

Hi !

Thanks for this plugin. I would love to use it, but not for existing users.

In fact, my SAAS website will have partnerships with some other website. Each time a new site is registered (paid one) on my SAAS that come from one of my partner, I would like to give the partner some money. Is it possible without creating him a user ?

How can I achieve what I want ?

Thanks !