multiple draw calls on same Texture2D with independent X and Y coordinates

Hello all!

I'm making a fishing game, however i've been stuck on my fishfinder code.

Im trying to make something like this: [http://www.youtube.com/watch?v=Bieo9wRABtk][1]

I shoot a ray from bottom of my boat to track the distance from it to Terrain = depth.

Then i use GUI.DrawTexture to draw one "pixel" to the GUI. This shall be the bottom of the lake, the distance from the top of the screen to the texture is equal with the distance from boat to the terrain... However i cant find way to draw multiple textures with the same texture and move them with independent x and y positions, so the screen actually "updates".

Here's my code

 var hit : RaycastHit;
 var echoPixel : Texture2D;
 var echoHit : RaycastHit;
 
 
 var pixelPosX = 210;
 var pixelPosY = 200;
 
 
 var fishDepth : float = 0.0f;
 
 var echoWindow : Rect = Rect(40,250,220,270);
 
 function Start () {
 
 }
 
 function Update () {
 
 var EchoSounder = gameObject.Find("EchoSounder").transform;
 
 var bottom = transform.position - Vector3(0,1,0); // define the boat's bottom
 
 Debug.DrawRay(bottom,-transform.up * 100, Color.red); // debug depth tracker
 
     if (Physics.Raycast(bottom,-transform.up,hit, 100)){ // depth tracking
         if (hit.transform.name == "Terrain"){
             depth = hit.distance;
         }
     
     }    
     
     Debug.DrawRay(EchoSounder.position,-transform.up * 100, Color.grey); // debug fish tracker
     
         if (Physics.Raycast(EchoSounder.position,-transform.up,echoHit, 100)){ // fish tracking
     
         if (echoHit.transform.tag == "Fish"){ // if fish found, set fishdepth
             fishDepth = echoHit.distance;
     
         }
     
     }    
 
 
 }
 
 function OnGUI(){
 
 echoWindow = GUI.Window(0, echoWindow, newWindow,"Fishfinder");
 
 }
 
 function newWindow(windowID: int){
 
 var pixMax = 250; // total vertical pixels of the screen
 var maxDepth = 20; // maxium depth 20 meters
 
 
 pixelPosY = depth / maxDepth * pixMax; // pixelPosY = convert the distance from the boat to the bottom to the screen. 
 
 GUI.DragWindow (Rect (0,0,10000,10000));
 
 
 GUI.Label(Rect(10,20,100,20),depth.ToString("f1")+ " Meters"); // display depth
 GUI.Label(Rect(10,40,100,20),"Fish at: "+ fishDepth.ToString("f1")+ " Meters"); // temporal fish display
 
 
 movePixel();
 
 
 
 if (pixelPosX < 11) // move the pixel to the begin of the screen
     pixelPosX = 210;
 
 
 }
 
 function movePixel()
 {
 var posX = pixelPosX;
 var posY = pixelPosY;
 for(var i = 210;i > 10;i--)
 {
 GUI.DrawTexture(Rect(posX,posY,1,250), echoPixel); // draw a pixel
 posX = posX - 1; // move the pixel
 }
 

If you have something to suggest i'll appreciate that. Thank you