Prevent user switching between login and signup


I’m moving our app over to new universal login.

One problem I have is that I need to check an activation code from the user before they are allowed to sign up.

I could do this from within my app and then open the signup page but I can’t work out how to prevent users switching to signup from the login page. Is there some way to hide the links that switch between the two pages?

The only solution I have found online is to disable signup but that’s not what I need.