| position | The rectangle the control should be shown within. | 
| mouse | The mouse cursor to use. | 
| controlID | ID of a target control. | 
Add a custom mouse pointer to a control.
	function OnGUI()
	{
		// show the "Link" cursor when the mouse is howering over this rectangle.
		EditorGUIUtility.AddCursorRect (Rect(10,10,100,100), MouseCursor.Link);		
	}