I need help creating a shortcode that I can use in the BACK END. In the Admin area.

Seriously, I have searched the web over. Every forum, every snippet I can find and nothing is working.
Can it be done? it HAS to be possible! How is the username displayed in the upper right corner of the admin area??

I have been able to create a shortcode, using a function code in functions.php and all works lovely on the front end.

but the back end?

I am simply wanting to welcome the new user into the backend. I am using the Ultimate Branding tool. I am using the Widget Tab, Custom Message, which creates a custom welcome message.

I want to place a shortcode in here so I can call the logged in user by name. That's it.