Gui Text popup, fade out

Hi there!

I would like some help with a script I'm working on. It's a battery pickup script, so when you pickup a battery a text pops up in the bottom left corner that says that you collected a battery.

I want it so when the text pops up it should fade out after a couple of seconds. Now they just stacks on top of each other by using an array.

Here's my Inventory script:

 var batteries = new Array();
 var guiSkin : GUISkin;
 
 function OnGUI()
 {
     for(var i : int = 0; i < batteries.length; i++)
     {
         GUI.skin = guiSkin;
         GUI.Label(new Rect(90, Screen.height - 60 - (i*60), 120, 50), ("Picked up Battery"), "HUD");
     }
 }

I hope you guys understand!