EW - cameraScroll

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(Camera))]

public class cameraScroll : MonoBehaviour {

    private float xvalorg;
    private float xvaldelta;

    public float scrollSpeed;

    Vector3 ThePosition;

    void Update () {
        if (Input.GetMouseButtonDown(0))
        {
            xvalorg = Input.mousePosition.x;
        }
        if (Input.GetMouseButton(0))
        {
            xvaldelta = Input.mousePosition.x;

            //if heigher than button area
            if (Input.mousePosition.y > 100f)
            {
                ThePosition = transform.position;
                ThePosition.x += (xvalorg - xvaldelta) * scrollSpeed;
                transform.position = ThePosition;
            }
            xvalorg = Input.mousePosition.x;
        }
    }
}