How to make Windows Authentication to work for only for spec

Question

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 SPECIFIC MEMBERS of my organization; for others it should not show a welcome message.

How can I achive this?