Help with formula - Not equal to multiple values

Hey there!

I have a page where I would like to only enable the button for a few users, so I am trying to create a formula to add to Button Options > Disable if:

User()!=([username])

It works well if I add just one user, but I will need to have 2 people allowed to click on the button. And I tried to add another user, like:
User()!=([username1,username2])

But it doesn’t work.
Any idea how can I add not equal to multiple values?

Thanks,