C# unity if statement logic

I recently started learning to code in C# for Unity; in the following script trying to enable and disable an object (enemy) based on the position of the mouse.

The problem is the code works fine in enabling the object, but I can't figure out how to disable it once it's been activated, so that the object appears and disappears as the mouse moves back and forth - in and out of range. Please let me know if you have a solution. Thank you!

using UnityEngine; using System.Collections;

public class Paddle : MonoBehaviour {

public GameObject enemy;

// Use this for initialization
void Start () {

    enemy.SetActive(false);
}

// Update is called once per frame
void Update () {

    Vector3 paddlePos = new Vector3 (8f,this.transform.position.y,0f); 

    float mousePosInBlocks = Input.mousePosition.x / Screen.width * 16;

    paddlePos.x = Mathf.Clamp(mousePosInBlocks, 6f, 8f);

    this.transform.position = paddlePos; 

        if (mousePosInBlocks < 6f) {
            print ("1");

        } else if(mousePosInBlocks <= 6.5f) {
            print("2");

            enemy.SetActive(true);


        } else if(mousePosInBlocks <= 7.5f) {
            print("3");

        } else {
            print("4");
    }
}

}