force translation

how can I force a movement transform.translate? I have a scene with an enemy that goes back and forth. I used Mathf.pingpong to bring you back. I want to make sure that every time you collide with something Invert its translation but is forced into Update. How can I do?

 

Code (csharp):

1.  
2. void FixedUpdate(){
3. transform.Translate(movementVector * direction);
4. }
5.  
6. void OnCollisionEnter(){
7. direction *= -1;
8. }
9.  

Something liek that?

 

This is what I want to accomplish, I hope you can understand it better