How to limit the Rotation of an object to 45 degrees.

Hello, I am building a car simulator for a school project and I want to make a steering wheel, the only problem is that it rotates too much and I need to limit it. Please help me!
Here is for rotating the wheel.

Code (JavaScript):

1.     public var moveSpeed : float = 10f;
2. public var turnSpeed : float = 50f;
3.  
4. function Update ()
5. {
6.  
7.  
8.     if (Input.GetAxis ("Horizontal") ==-1)
9.  
10. transform.Rotate(Vector3(0,0,a), -turnSpeed * Time.deltaTime);
11.  
12.     if (Input.GetAxis ("Horizontal") ==1 )
13.             transform.Rotate(Vector3.forward, -turnSpeed * Time.deltaTime);