Right Click --> Display Settings --> Security Code
You can make a screen to have code "C", for example
In Security Model, only make the Groups (or users) that you want to access the screen have code "C".
They will have to be logged in to the system then to see that screen.
Alternatively, whatever navigation button goes to the screen you can have "CurrentUserHasCode( C )" on the "enable" section (if using FTVSE 8.0) or for visibility or whatever model you use.