How to make Windows Authentication to work for only for specific members in the organization?

I am creating an Intranet Website which uses Windows Authentication.
I want to use it for only certain specific members of my organization. I have a line of code in my _LogOnPartial.cshtml page
    <text>Welcome <strong>@User.Identity.Name</strong>!     [ @Html.ActionLink("Log Off", "LogOff", "Account") ]</text>
But when my manager runs the website from my organization he will see a welcome message like - Welcome MYORGANIZATIONDOMAIN\MyManagersUserName,
when my fried runs it from my organization he will see a message like - MYORGANIZATIONDOMAIN\FriendsUserName,
anyone accessing the website will see the welcome message with the user name.
I DON'T WANT this to happen. I want to show the welcome message only to CERTAIN SPEC ...