// Sets an Occlusion area of 10 units in x, 20 units in y and 30 units in z

@script RequireComponent(OcclusionArea)

transform.GetComponent(OcclusionArea).size = Vector3(10,20,30);

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(OcclusionArea))]
public class example : MonoBehaviour {
    void Example() {
        transform.GetComponent<OcclusionArea>().size = new Vector3(10, 20, 30);
    }
}

import UnityEngine
import System.Collections

[RequireComponent(OcclusionArea)]
class example(MonoBehaviour):

    def Example():
        transform.GetComponent[of OcclusionArea]().size = Vector3(10, 20, 30)