Return First Window

Hello,

How can i return the first window from the last window while using the commonjs navigation window ?

Thanks

app.js

var StartUp = require('/control/startUp');
StartUp.StartApp();

function StartApp() {
    'use strict';
    var MainWin,
        OpenBtn,
        navGroup;
 
    MainWin = Titanium.UI.createWindow({
        backgroundColor : '#FFF',
 
        title : 'Main Window'
    });
 
    var label = Ti.UI.createLabel({
        text:'First Window',
        color:'#000',
 
    });
    MainWin.add(label);
 
    OpenBtn = Ti.UI.createButton({
        title : 'Open Win',
        width : 30,
        top : 50,
        left : 150,
        height : 25,
        color : '#990000',
        style : Ti.UI.iPhone.SystemButtonStyle.PLAIN
    });
 
    navGroup = Ti.UI.iOS.createNavigationWindow({
        window : MainWin
    });
 
    MainWin.containingNav = navGroup;
 
    OpenBtn.addEventListener("click", function(e) {
        var NewWin = require("/ui/winTwo").WinTwo();
        NewWin.containingNav = navGroup;
        navGroup.openWindow(NewWin);
    });
 
    MainWin.setRightNavButton(OpenBtn);
 
    navGroup.open();
};
 
exports.StartApp = StartApp;

winTwo.js

function WinTwo() {
    'use strict';
    var MainWin,
        OpenBtn;
 
    MainWin = Ti.UI.createWindow({
        backgroundColor : '#FFF',
        titleControl:Ti.UI.createLabel({
            text:'Window 2',
            color:'#000'
        }),
        title:'Window 2'
    });
 
    OpenBtn = Ti.UI.createButton({
        title : 'Open 3rd Win',
        width : 30,
        top : 50,
        left : 150,
        height : 25,
        color : '#990000',
        style : Ti.UI.iPhone.SystemButtonStyle.PLAIN
    });
 
    var label = Ti.UI.createLabel({
        text:'Window 2',
        color:'#000'
    });
    MainWin.add(label);
 
    MainWin.setRightNavButton(OpenBtn);
    OpenBtn.addEventListener("click", function(e) {
 
        var NewWin = require("/ui/winThree").WinThree();
        NewWin.containingNav = MainWin.containingNav;
        NewWin.containingNav.openWindow(NewWin);
 
    });
 
    return MainWin;
 
}
 
exports.WinTwo = WinTwo;

function WinThree() {
    'use strict';
    var MainWin,
        OpenBtn;
 
    MainWin = Ti.UI.createWindow({
        backgroundColor : '#FFF',
        titleControl:Ti.UI.createLabel({
            text:"Window 3"
        }),
        title:'Window 3',
        color:'#000'
    });
 
    var label = Ti.UI.createLabel({
        text:'Window 3',
        color:'#000'
    });
 
    OpenBtn = Ti.UI.createButton({
        title : 'open 4nd Win',
        width : 30,
        top : 50,
        left : 150,
        height : 25,
        color : '#990000',
        style : Ti.UI.iPhone.SystemButtonStyle.PLAIN
    });
 
    MainWin.setRightNavButton(OpenBtn);
    OpenBtn.addEventListener("click", function(e) {
 
        var NewWin = require("/ui/winFour").WinFour();
        NewWin.containingNav = MainWin.containingNav;
        NewWin.containingNav.openWindow(NewWin);
 
    });
 
 
    MainWin.add(label);
 
 
 
 
    return MainWin;
 
}
 
exports.WinThree = WinThree;

function WinFour() {
    'use strict';
    var MainWin,
        OpenBtn;
 
    MainWin = Ti.UI.createWindow({
        backgroundColor : '#FFF',
        titleControl:Ti.UI.createLabel({
            text:"Window 4"
        }),
        title:'Window 4',
        color:'#000'
    });
 
    var label = Ti.UI.createLabel({
        text:'Window 4',
        color:'#000'
    });
    MainWin.add(label);
    label.addEventListener("click",function(){
        MainWin.close();
    });
 
 
 
    return MainWin;
 
}
 
exports.WinFour = WinFour;