Raycast layer mask problem

Hi all, I am somewhat new to unity but think I have a good understanding of how things work.

My basic problem is that I want to use a layer mask with

 Camera.main.ScreenPointRoRay

I am using a Physics.RayCast from my camera to my player to detect if anything is in the way, if it is then I am hiding it so we can see the player through it using:

 camHit.transform.renderer.enabled = false;

This works fine, but once it's hidden I want to use a layermask so my click to move function works properly (this is what uses the Camera.main.ScreenPointRoRay), otherwise my ray hits the object in the ways collider.

If I disable the object I hit collider my Physics.Raycast hits the player and so hides the object again, then unhides, and loops forever.

I may have gone about doing this in the completely wrong manner, hopefully someone can assist.

Here is my function for detecting if objects are in the way.

 function hideObjects()
 {
 var camHit : RaycastHit;
 var fwd = Camera.main.transform.TransformDirection(Vector3.forward);
 if(Physics.Raycast(Camera.main.transform.position, fwd, camHit, 50))
 {
 print(camHit.transform.tag);
 if(camHit.transform.tag == "roof")
 {    
     theRoof = camHit.transform;
     camHit.transform.renderer.enabled = false;
     camHit.transform.collider.enabled = false;
 }
 else if (camHit.transform.tag == "player")
 {
     theRoof.renderer.enabled = true;
     theRoof.transform.collider.enabled = true;
 }
 }
 Debug.DrawLine (Camera.main.transform.position, camHit.point, Color.yellow, 0.25);
 
 }

and here is a snippet of my click to move function. This is the Ray that will hit the building collider, this is the function I want to put a layer mask on but I don't know how judging by the options on this page:

http://docs.unity3d.com/Documentation/ScriptReference/Camera.ScreenPointToRay.html

             if(Input.GetKeyDown(KeyCode.Mouse0))
             {
                 var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
                 //MOVEMENT CODE HERE
             }

Thanks in advance :)

Mike