Get User from a text field

I am trying to make a form a little more user friendly and eliminate unnecessary data entry.  The field I am trying to automate now is an email address that will be used for notifications.  Is there a way to dynamically populate an email address from a text field that has the users first and last names.  The source data is not generated in Quick Base. 

The current form structure has a User field that allows the user to select a user from the app's users.  Another field uses the UserToEmail function to get the email address for the notification.  I would like to eliminate this step if possible.  The desired source field is not a Quick Base user at any point.  I'm not sure if this is important; but, the field is a lookup field from a parent table. I haven't found a function that would match a user with a text field.  

Is this possible?