GUI.Window Set pos after runtime

So I am running into a problem where I cannot set the position of a window after I have ran the program. I have tried delcaring it in the OnGUI function, but then it is static and not draggable (probally somthing to do with that) but just wondering if anyone knows how to set a GUI.Window to select X, Y.

  var screenX : int;

  var screenY : int;

  var windowRect0 : Rect = new Rect(screenX, screenY, 100, 100);

  function OnGUI () {

   screenX = Screen.width*2/3;

   screenY = Screen.height/2;

   Debug.Log(windowRect0);

   windowRect0 = GUI.Window (0, windowRect0, DoMyWindow, "Inventory");

But it is spawning at 0, 0, top left no matter what i change in the script. And if I put the var in the OnGUI function I cannot drag it.