iTween - How to move an object that is currently undergoing a "tweening"?

I have a sphere, that goes up and down in a loop. I’m doing it as following via iTween:

iTween.MoveTo(gameObject, new Hashtable
                                  {
                                      {"position", transform.position - new Vector3(0, 20, 0)},
                                      {"time", 1},
                                      {"easetype", iTween.EaseType.easeInOutSine},
                                      {"looptype", iTween.LoopType.pingPong}
                                  });

It works fine alright.

The problem is I can no longer move this sphere.
I want to move the sphere around my stage while it is going up and down.

I took a step back and re-analysed my problem.
The problem I have reduced to the simplest form is: How do I have two animations that interact on the same object?

MoveAdd was the function I needed, as it doesn’t take a snapshot of the initial position.
I think I should leave this question here in case someone bumps into the same problem as me.