Rotation using mouse

how can i make a area in the screen to where the mouse will not cause the player rotate

C#

using UnityEngine;
using System.Collections;

public class MouseLook : MonoBehaviour {

public float mouseLook = 1.0f;
public int edgeBoundry = 10;

// Use this for initialization
void Start () {

}

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

	if(Input.GetKey(KeyCode.Escape)){

		Application.Quit();

	}

	if (Input.mousePosition.x < Screen.width / edgeBoundry) {
		
		if (transform.position.z > -4) {
			
			transform.Rotate (Vector3.down * mouseLook);

		}
	}

	if (Input.mousePosition.x > Screen.width / edgeBoundry) {

			if(transform.position.z < 8){
				
				transform.Rotate(Vector3.up * mouseLook);
		
			}
		}

	if (Input.mousePosition.x > Screen.width / edgeBoundry) {
		
		if(transform.position.z > -4 || transform.position.z < 8){
			
			transform.Rotate(Vector3.zero);
			
		}
	}

}

}

First of all, your way of setting the area largely depends on the screen resolution, which is completely different depending on the user.

There are many ways you can do this. And it really depends on the shape of the area. One way off the top of my head is to use GUI. You can make the GUI invisible and and when the mouse is over it, set a boolean to not rotate.