Tooltip and mouse position

Hi all I had actually posted to another answer and mean to start a question of my own, I am very new to scripting I( am a game artist looking to get into the intricacies of scripting and boought unity several years back when you had to purchase an indie license, I am now starting on making a game and I know that my scripting is very basic but I had taken some examples from here to try and create a tooltip that appears at the mouse when you hover over the object, in this case a button. However when the moueover occurs the tooltip is at the bottom of the screen, I learn better if I know what was wrong could anyone explain to me why my code isnt working and help me get it right? Its intimidatying being new to this type of thing and I hope it does not seem like a dumb question...Here is the code

 var mousePos: Vector3 = Input.mousePosition;

function OnGUI () {
        if (GUI.Button (Rect (10, 10, 100, 50), GUIContent("New Game", "Start a  New Game")))
        {

        Application.LoadLevel (1);

        }
        GUI.Label (Rect (mousePos.x, mousePos.y - 100, 100, 20), GUI.tooltip);
}

OnGUI code should use Event.current.mousePosition, not Input.mousePosition (using Input results in screen space coords, not GUI coords). You can't just declare it once, you need to get the position every frame, so it has do be done in OnGUI.

You can use this script

var mousePos: Vector2;

function Update ()
{
   mousePos  = Input.mousePosition;
}

function OnGUI () 
{
    if (GUI.Button (Rect (10, 10, 100, 50), GUIContent("New Game", "Start a  New Game")))
    {
       Application.LoadLevel (1);
    }
    GUI.Label (Rect (mousePos.x, mousePos.y -100, 100, 20), GUI.tooltip);
}

Hi Erich thanks for your answer I am trying via your advice to complete the script and for aome reason now that I am calling the mousePosition in the OnGUI function it is not showing this is the current code I am using thanks again....

 var mousePos: Vector2 ;

    function OnGUI () {

            mousePos = Event.current.mousePosition;

            if (GUI.Button (Rect (10, 10, 100, 50), GUIContent("New Game", "Start a New Game")))
            {
            Application.LoadLevel (1);
            }
            GUI.Label (Rect (mousePos.x, mousePos.y - 100, 100, 20), GUI.tooltip);
    }

Update I changed the structure a bit Erich thanks to your help its seems to be working, thank you to all who answered I really appreciate it !! PS I tried to login to say your answer helped me but it wont let me login under any of my IDs....weird...