Reverse moving left and right script [c#]

Well, basically I am new to Unity - and currently working on my very first Unity 2D game. I have an object that is moving left and right (automated), and I need to have another object moving the opposit way. Which means I have to reverse my current script, so instead of having the object moving from left to right, and back to left - I need it to start from right, move to left - and back to right. Here is the code I have now:

 public float speed;
     public float distance;
     private float xStartPosition;
     void Start () {
         xStartPosition = transform.position.x;
     }
     void Update () {
         if ((speed < 0 && transform.position.x < xStartPosition) || (speed > 0 && transform.position.x > xStartPosition + distance))
         {
             speed *= -1;
         }
         transform.position = new Vector2(transform.position.x + speed * Time.deltaTime, transform.position.y);
     }

Help would be much appreciated. I have tried to search Google etc, but decided to submit my problem here. Thanks in advance.