Best way to unlock levels as you go?

Hi, I seem to be very stumped on this. I can't create a script that will hide my button (it's not GUI) when the level is locked. Then, I want to be able to unlock the button when Level1 is passed, so they can continue to Level2. Any help is much appreciated! Also, I have buttons named Level2, and LockedLevel2. How would I display LockedLevel2, when level one was beaten, as well as displaying Level2 when it was beaten?

 

gameObject.renderer.enabled = false;

Simple:
http://forum.unity3d.com/threads/level-unlock-system.153184/

Video (dint look at it)

 

Thanks a lot, really appreciated. Works well.