setEnabled() et QLabel

#ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>

namespace Ui {
    class Dialog;
}

class Dialog : public QDialog
{
    Q_OBJECT

public:
    explicit Dialog(QWidget *parent = 0);
    ~Dialog();

public slots:
    void Check();
    void Unlock();
private:
    Ui::Dialog *ui;
};

#endif // DIALOG_H

#include "dialog.h"
#include <QString>
#include <QtGui>
#include "ui_dialog.h"
#include <QMessageBox>

Dialog::Dialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::Dialog)
{
    ui->setupUi(this);
    ui->Mdp->setEchoMode(QLineEdit::Password);
ui->boutonUnlock->setEnabled(false);
    this->showFullScreen();
    QObject::connect(ui->boutonUnlock,SIGNAL(clicked()),this,SLOT(Unlock()));
    QObject::connect(ui->boutonCheck,SIGNAL(clicked()),this,SLOT(Check()));
}

void Dialog::Check()
{
    QLineEdit Mdp;
    QPushButton boutonUnlock;
    QLabel labelCheck;
if(Mdp.text() == "monmotdepasse")
    {
labelCheck.setText("Mot de passe Correct");
boutonUnlock.setEnabled(true);
}
else {
    labelCheck.setText("Mot de passe Erroné");
}
}

void Dialog::Unlock()
{
    Dialog w;
    QLineEdit Mdp;
if(Mdp.text() == "monmotdepasse")
    {
this->close();
}
else {
    QMessageBox::critical(this,"Erreur","Le mot de passe que vous avez entré est incorrect");
}
}

Dialog::~Dialog()
{
    delete ui;
}

#include <QtGui/QApplication>
#include "dialog.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Dialog w;
    w.show();

    return a.exec();
}