How to add/update User field under Portfolio Items menu

Under Portfolio Items view, there is a field to assign a User name to an asset i.e. the main user of the portfolio item) which is linked to the User link from AMEMPLDEPT table. Currently, it assigns the user dependingon the UserName i.e. Last Name and First Name format e.g. LASTNAME,FIRSTNAME format. Need this to be changed to ADID format i.e. AD\abcd12345