Acceder una variable fuera de una funcion?

[riahc3]

Buenas

Tengo esto:

Código:

<script type="text/javascript">

                /*
 * Copyright 2010 Nicholas C. Zakas. All rights reserved.
 * BSD Licensed.
 */
function CrossDomainStorage(origin, path){
    this.origin = origin;
    this.path = path;
    this._iframe = null;
    this._iframeReady = false;
    this._queue = [];
    this._requests = {};
    this._id = 0;
}

CrossDomainStorage.prototype = {

    //restore constructor
    constructor: CrossDomainStorage,

    //public interface methods

    init: function(){

        var that = this;

        if (!this._iframe){
            if (window.postMessage && window.JSON && window.localStorage){
                this._iframe = document.createElement("iframe");
                this._iframe.style.cssText = "position:absolute;width:1px;height:1px;left:-9999px;";
                document.body.appendChild(this._iframe);

                if (window.addEventListener){
                    this._iframe.addEventListener("load", function(){ that._iframeLoaded(); }, false);
                    window.addEventListener("message", function(event){ that._handleMessage(event); }, false);
                } else if (this._iframe.attachEvent){
                    this._iframe.attachEvent("onload", function(){ that._iframeLoaded(); }, false);
                    window.attachEvent("onmessage", function(event){ that._handleMessage(event); });
                }
            } else {
                throw new Error("Unsupported browser.");
            }
        }

        this._iframe.src = this.origin + this.path;

    },

    requestValue: function(key, callback){
        var request = {
                key: key,
                id: ++this._id
            },
            data = {
                request: request,
                callback: callback
            };

        if (this._iframeReady){
            this._sendRequest(data);
        } else {
            this._queue.push(data);
        }   

        if (!this._iframe){
            this.init();
        }
    },

    //private methods

    _sendRequest: function(data){
        this._requests[data.request.id] = data;
        this._iframe.contentWindow.postMessage(JSON.stringify(data.request), this.origin);
    },

    _iframeLoaded: function(){
        this._iframeReady = true;

        if (this._queue.length){
            for (var i=0, len=this._queue.length; i < len; i++){
                this._sendRequest(this._queue[i]);
            }
            this._queue = [];
        }
    },

    _handleMessage: function(event){
        if (event.origin == this.origin){
            var data = JSON.parse(event.data);
            this._requests[data.id].callback(data.key, data.value);
            delete this._requests[data.id];
        }
    }

};


var remoteStorage = new CrossDomainStorage("http://algo.com", "/server.html");
                    remoteStorage.requestValue("unallave", function(key, value){
                    alert("El valor para '" + key + "' es '" + value + "'");

                    });

                    alert ("Quiero accerder value aqui! " + value);
    </script>

Creo que es auto explicatorio y es una pregunta MUY tonta :( y de novato: Quiero acceder value fuera de esa funcion. Haciendo algo como:

Código:

var unavariable="";
var remoteStorage = new CrossDomainStorage("http://algo.com", "/server.html");
                    remoteStorage.requestValue("unallave", function(key, value){
                    alert("El valor para '" + key + "' es '" + value + "'");
                    unavariable=value;
                    });
                   alert ("probamos " + unavariable);

Código:

var unavariable="";
var remoteStorage = new CrossDomainStorage("http://algo.com", "/server.html");
                    unavariable=remoteStorage.requestValue("unallave", function(key, value){
                    alert("El valor para '" + key + "' es '" + value + "'");
                    return value;
                    });
                   alert ("probamos " + unavariable);

Tampoco funciona. Ninguna de las dos. Como puedo lograr lo que quiero? Gracias!