Showing a layer with GUI Box(Behind layer) on click of game Object

I have 2 layers on the current scene,One which is visible by default and contain certain GameObjects and custom layer which appear only when those GameObjects are clicked. When this custom Layer appears ,A GUI.BOX should appear behind this layer.But what happens currently is,GUI.Box appears on top of everything. While searching for solution, there are certain links which says create another camera and set clear flags to depth Only,Culling Mask to that layer ,Which I did ,but it shows GUI.Box above every layer.

You can do this by taking another camera for custom layer, then call
2ndCamera.Render() at last line of GUI() method where you have defined GUI.Box().

This will render camera’s 3D view on GUI of 1st camera.