I would like to hide some folders for some users :

|____Sub Folder2
|____Sub Folder3

For example, I want user "John" to have access to Folder1, but I don't
want him to see Sub Folder3
How do I make this?

What i've done :
Put a trustee on Folder 1, where John has full access
Put an explicit trustee on Sub Folder3, where John has no right.

It worked for one time, but it does not work anymore!John can see
everything in Folde1
Any help?Is there a better way to do this?