OnTriggerEnter change GuiText problem

Hi there,
I have made the following script but something wrong with the code

function OnTriggerEnter (myTrigger : Collider) 

I have linked this script into a Guitext
Then when the fuction runs i am getting the following error:

MissingComponentException: There is no 'GUIText' attached to the "Sphere_U" game object, but a script is trying to access it.
You probably need to add a GUIText to the game object "Sphere_U". Or your script needs to check if the component is attached before using it.
Scorescript+$OnTriggerEnter$22+$.MoveNext () (at Assets/Scripts/Scorescript.js:28)

What’s my error? The Spere_U is the object that my player touch and the function activated
Thx in advance!!

The output says it all. A GUIText is a component you can add from the toolbar Components->Rendering->GUI Text. If the GameObject your script is attached to doesn’t have that component doesn’t have a GUIText, guiText (which is a shortcut for GetComponent.< GUITex >()) will return null.