A button to send an interactive form to a given email address in a form field

I am trying to create as form that has several stages of approval. The first person will fill out some of the form fields, then click a button to send it onto the next person. The second person will then fill in the other half of the form and send for approval.

I have this down no problem, but I am then trying to have the third person send the form on for second approval to an email address that they themselves enter into one of the form fields. Is this possible at all? Or does the email recipient need to be pre-determined?

I am using Acrobat Pro DC on Windows 7 Professional but need this form to be usable by those with standard Acrobat Reader as well.

Any help would be much appreciated!