OnDrag does not stop to detect screen bounds

I have a GUI window with a OnDrag event function. The thing is, I want the GUI window to stop when it touches any of the screen boundaries. Is that possible? Can someone please show me how do I go about doing something like this?

Here is the code that handles the "drag" event:

 /// <summary>
         /// Called by the EventSystem everytime the pointer is moved during dragging
         /// </summary>
         /// <param name="eventData">The current event data</param>
         public void OnDrag(PointerEventData eventData)
         {
             GUIRectTransform.position = eventData.position - mCursorOffset;
         }
 
         /// <summary>
         /// Evaluates the current state and transitions to the pressed state
         /// </summary>
         /// <param name="eventData">The EventData usually sent by the EventSystem</param>
         public void OnPointerDown(PointerEventData eventData)
         {
             Vector2 dragBegin;
             RectTransformUtility.ScreenPointToLocalPointInRectangle(GUIRectTransform, eventData.position, eventData.pressEventCamera, out dragBegin);
             Vector2 rectPosition = GUIRectTransform.position;
             mCursorOffset = eventData.position - rectPosition;
         }
 
         /// <summary>
         /// Evaluate eventData and transition to appropriate state. New state will be based upon current hover state.
         /// </summary>
         /// <param name="eventData">The EventData usually sent by the EventSystem.</param>
         public void OnPointerUp(PointerEventData eventData)
         {
             //TODO: Add logic here
         }