Set a relative (custom) speed to a rotation

I am making a character rotate around its axis using euler angles. Not quite as transform.Rotate that makes the character fall through the terrain. But I want it to put a custom speed. I mean a float or something that can be edited in the script for the character to rotate at a speed I want to set in the script.

 if (((Input.GetAxis("Horizontal") > deadZone) && !Input.GetKey(KeyCode.LeftShift)) ||
(Input.GetAxis("Horizontal") < -deadZone) && !Input.GetKey(KeyCode.LeftShift))
transform.eulerAngles += new Vector3 (0, Input.GetAxis("Horizontal"), 0);

It means that if i press the left or right inputs, the character rotates around its y axis. Now i have to set its speed. How could I set a relative speed to it???

Like this:

    if (((Input.GetAxis("Vertical") > deadZone) && !Input.GetKey(KeyCode.LeftShift)) ||
        (Input.GetAxis("Vertical") < -deadZone && !Input.GetKey(KeyCode.LeftShift)))
        TP_Motor.Instance.MoveVector += new Vector3(0, 0, Input.GetAxis("Vertical"));

This is the other code from the other script:

public Vector3 MoveVector { get; set; }
public float VerticalVelocity { get; set; }

void Awake () 
{
    Instance = this;
}


public void UpdateMotor () // Le cambie era UpdateMotor
{
    ProcessMotion();
}

void ProcessMotion()
{

// First Movevector

    // Transform MoveVector to worldspace
    MoveVector = transform.TransformDirection(MoveVector);

    // Normalize MoveVector if Magnitude > 1
    if (MoveVector.magnitude > 1)
        MoveVector = Vector3.Normalize(MoveVector);

    // Multiply MoveVector by MoveSpeed
    MoveVector *= MoveSpeed();

    // Reapply VerticalVelocity MoveVector.y
    MoveVector = new Vector3(MoveVector.x, VerticalVelocity, MoveVector.z);

    // Apply Gravity
    ApplyGravity();

    // Move the character into world space
    TP_Controller.CharacterController.Move(MoveVector * Time.deltaTime);
   
}

If you want to rotate at a certain speed depending on your horizontal axis, set a speed to base your input on:

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour
{
	float speed = 3.0f;
	
	void Update()
	{
		transform.localEulerAngles += new Vector3(0, Input.GetAxis ("Horizontal") * speed * Time.deltaTime, 0);
	}
}