Placing buildings

I would like to have a script, where if you have a certain amount of logs and stones, you can create a campfire. I want a raycast from the middle of the screen to hit a colldier, and instantate a prefab. I then want this prefab to follow the raycast's position, but all my efforts so far have failed. I will post the code for both of these scripts, the GUI and the handler. Builder_GUI.js #pragma strict

 private var WindowLoc : Rect = Rect(Screen.width/4, Screen.height/4, Screen.width /2, Screen.height /2);
 private var scrollBarChopGrid : Vector2 = Vector2.zero;
 private var ShowBuildingMenu : boolean = false;
 private var Building_Handler : Building_Handler;
 
 var ToggleBuild : KeyCode = KeyCode.P;
 
 function Start()
 {
     Building_Handler = GetComponent("Building_Handler");
 }
 
 function Update()
 {
     if (Input.GetKeyDown(ToggleBuild))
         if (ShowBuildingMenu)
         {
             ShowBuildingMenu = false;
             
         }
         else
             ShowBuildingMenu = true;
 }
 
 function OnGUI () {
     if (ShowBuildingMenu)
         WindowLoc = GUI.Window(0, WindowLoc, Building_Selection, "");
 }
 
 function Building_Selection(windowID : int)
 {
     GUI.Label(Rect(5, 0,100,25), "<b>Item to build:</b>");
     GUI.Label(Rect(110, 0,200,25), "<b>Resources required:</b>");
     scrollBarChopGrid = GUI.BeginScrollView(Rect (0, 25, Screen.width/2,257), scrollBarChopGrid, Rect(0,0,0,500));
         
         GUI.Label(Rect(5, 0,100,25), "Camp Fire");
         GUI.Label(Rect(110,0,200,25), "10xWood, 10xStone");
         if (GUI.Button(Rect(315, 0,75,25), "Build"))
         {
             Building_Handler.Building = true;
             Building_Handler.Once = true;
             ShowBuildingMenu = false;
         }
     GUI.EndScrollView();
 }

Building_Handler.js

 #pragma strict
 
 @HideInInspector
 var Building : boolean = false;
 var BuildCampFire : GameObject;
 
 @HideInInspector
 var Once : boolean = false;
 
 private var hitPointX : int = 0;
 private var hitPointY : int = 0;
 private var hitPointZ : int = 0;
 
 function Update () {
     if (Building)
     {
         var ray : Ray = Camera.main.ScreenPointToRay(Vector3(Screen.width*0.5, Screen.height*0.5, 0));
         var hit : RaycastHit;
         if(Physics.Raycast (ray, hit, 50))
         {
             var clone : GameObject;
             hitPointX = hit.point.x;
             hitPointY = hit.point.y;
             hitPointZ = hit.point.z;
             if (Once)
             {    
                 clone = Instantiate(BuildCampFire, Vector3(hitPointX,hitPointY + 0.5,hitPointZ), Quaternion.Euler(0,0,0));
                 Once = false;
             }
             clone.position = Vector3(hitPointX,hitPointY,hitPointZ);
             
             if (Input.GetMouseButtonDown(0))
             {
                 Building = false;
             }
         }
     }
 }

Please reply quickly, so I can get this annoying problem fixed.

Thanks!

Stormy102