How to make a smooth zoom camera script with maximums?

I implemented this piece of code in my camera script, and it works fine, but how can I make a min - max zoom setting, and how can I make it that when I zoom in, it zooms in just a little bit further, like a zoom fade in and fade out. It needs to be smooth. Thank you!
using UnityEngine;
using System.Collections;

public class Zoom : MonoBehaviour {
	public float zoomSpeed = 20;
	void Update () 
		float scroll = Input.GetAxis("Mouse ScrollWheel");
		if (scroll != 0.0f)
			camera.fieldOfView -= scroll*zoomSpeed;

Do something like this:

float currentFOV = camera.fieldOfView

camera.fieldOfView = Mathf.Lerp(currentFOV, scroll, Time.time * zoomSpeed);

I didn’t test this out, but it should do the trick