Save Scene with Every Change - Help!

Hello everyone, I have this script from Unity Reference. it works fine but saves every min. how can i make it save every time a change is been made? for example if you pickup an item, after loading, the item not to be there anymore. So i can keep the changes in the scene.

class SimpleSaveScene extends EditorWindow{

var saveTime : float = 300;

var nextSave : float = 0;


@MenuItem ("Simple autoSave")

static function Init(){

	var window : SimpleSaveScene =

		EditorWindow.GetWindowWithRect(

		SimpleSaveScene,

		Rect(0,0,165,40));

	window.Show();


}


function OnGUI(){

EditorGUILayout.LabelField("Save Each:", saveTime + "Secs");

var timeToSave : int = nextSave - EditorApplication.timeSinceStartup;

EditorGUILayout.LabelField("Next Save:",timeToSave.ToString()+"Secs");

this.Repaint();



if(EditorApplication.timeSinceStartup > nextSave){

var path : String = EditorApplication.currentScene.Split(char.Parse(“/”));

path[path.Length -1] = "Autosave_" + path[path.Length-1];

 EditorApplication.SaveScene(String.Join("/",path), true);

Debug.Log("Saved Scene");

nextSave = EditorApplication.timeSinceStartup + saveTime;
}

}

}

Thank you in advance and for your time

Maybe this can help you…http://docs.unity3d.com/Documentation/ScriptReference/GUI-changed.html?from=EditorUtility