J2ME handing multiple pages

I have 1 midlet and 1 form. How do i make my display of the midlet when users pressed the back command from the form class? Thanks for helping!!

Midlet codes

import javax.microedition.midlet.*; import javax.microedition.lcdui.*;

public class LoginMidlet extends MIDlet implements CommandListener {

private newUser Login;
private Form form;
private Display display;
private TextField username, pwd;
private Command login;
private Ticker welcome;

public void startApp() {

    form = new Form("Welcome");
    welcome = new Ticker("Advertisments");
    form.setTicker(welcome);
    username = new TextField("Username :", null, 40, TextField.ANY);
    pwd = new TextField("Password :", null, 20, TextField.PASSWORD);
    form.append(username);
    form.append(pwd);
    login = new Command ("Login",Command.OK,1);
    form.addCommand(login);
    form.setCommandListener(this);
    display = Display.getDisplay(this);//get the display manager
    display.setCurrent(form);
}

public void commandAction(Command c, Displayable d) {
    if (c == login) {
        Form Login = new newUser("Register Account");
        display = Display.getDisplay(this);
        display.setCurrent(Login);
    }

}

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}

} Form class

import javax.microedition.midlet.*; import javax.microedition.lcdui.*;

public class newUser extends Form implements CommandListener {

private LoginMidlet midlet;
private Display display;
private StringItem welcome;
private Form form;
private Command cmdRegister, cmdBack;
private TextField username, password, email, address, mobile, confirmPassword;

public newUser(String title) {

    super(title);
    this.welcome = new StringItem(null, "Please enter the following information ");
    append(this.welcome);
    this.username = new TextField("Username :", null, 40, TextField.ANY);
    this.password = new TextField("Password :", null, 20, TextField.PASSWORD);

    append(this.username);
    append(this.password);

    this.cmdRegister = new Command("Register", Command.OK, 1);
    this.cmdBack = new Command("Back", Command.BACK, 0);
    addCommand(this.cmdBack);
    addCommand(this.cmdRegister);
    this.setCommandListener(this);
}

public void commandAction(Command c, Displayable d) {
    String label = c.getLabel();
    if (label.equals("Back")) {
        this.display = Display.getDisplay(this.midlet);




    }
    if (label.equals("Register")) {
    }
}

}