how can i put button to stop this movie?

hello ; my main problem is because of i have to define var www = new WWW(url) into function i can’t access from another function like OnGUI().

var url = "http://www.unity3d.com/webplayers/Movie/sample.ogg";
function Start () {
    // Start download
    var www = new WWW(url);

    // Make sure the movie is ready to start before we start playing
    var movieTexture = www.movie;
    while (!movieTexture.isReadyToPlay)
        yield;


    // Initialize gui texture to be 1:1 resolution centered on screen
    guiTexture.texture = movieTexture;

    transform.localScale = Vector3 (0,0,0);
    transform.position = Vector3 (0.5,0.5,0);
    guiTexture.pixelInset.xMin = -movieTexture.width / 2;
    guiTexture.pixelInset.xMax = movieTexture.width / 2;
    guiTexture.pixelInset.yMin = -movieTexture.height / 2;
    guiTexture.pixelInset.yMax = movieTexture.height / 2;

    // Assign clip to audio source
    // Sync playback with audio
    audio.clip = movieTexture.audioClip;

    // Play both movie & sound
    movieTexture.Play();
    audio.Play();
}
// Make sure we have gui texture and audio source
@script RequireComponent (GUITexture)
@script RequireComponent (AudioSource)

Just move the variable out of the function scope so it becomes a member variable.

var www : WWW;
var movieTexture : MovieTexture;
function Start () {
    www = new WWW(url);
    movieTexture = www.movie;

Something like this?

void OnGUI()
{
    string label = movieTexture.isPlaying ? "Pause" : "Play";
    if(GUILayout.Button(label))
    {
        if(movieTexture.isPlaying)
        {
            movieTexture.Pause();
        }
        else
        {
            movieTexture.Play();
        }
    }
}

Then define it outside of the Start function, like this:

var movieTexture : MovieTexture;
function Start () {
    www = new WWW(url);
    movieTexture = www.movie;
    // ... rest of the code.

That way, both functions can use it!