Create formula User field using another user field

Hello. 

I have an analyst field-user and leadership field-formula user. All users are QB users.

For Leadership field, I created a formula to say something along the lines of
If ([Analyst]=ToUser("analyst#1 email address"), "supervisor#1 email address",[Analyst]=ToUser("analyst#2 email address"), "supervisor#2 email address")

However this formula did not work... Does anyone have any idea how to make this work?

Thank you in advance!