I'd like to have your insights in solving an automation procedure. We have created a custom-field of a referral person, so every time a person is touching base with us after receiving our details by word-to-mouth,  not only we create a new Person, we also indicate the name of the person who referred that lead to ys. For example, if John Doe contacting us, we indicate that Sarah Smith referred John to us in that custom field.  What we want to automate is a thank-you workflow, so every time we update the referral person details, PD will send a Thank you email to Sarah, and not John. (Needless to say that we always update the referrals details, including email address prior to attaching the names when necessary)