Automatically add a comment base on field value

Hi everyone

I am looking for a VBA or macro which will take a persons "username" and add a cell comment into a separate sheet with their email address.
I have attached a sample work book with what I would like to happen automatically.
The comment will be added into the job roles sheet and it will obtain the data from the user sheet.

Most of the other threads want extra things to happen but I cannot work out the VBA script to simplify it for my own needs.

Many thanks in advance!