Connecting qprocess and qprogressdialogue

Sirs
I am having a problem with something that is so blindingly obvious I can't see it!
I want to connect a running external process to a progress dialogue that closes when the process finishes, or by pressing the cancel button on the dialogue stops the process.
Program so far:

Code:

void MP3collection::normalise()
{
    if ( check4normalise() )
    {
        infoWarnError(INFORMATION, nice("Normalise"), nice(QString("%1 already normalised").
                                                           arg(ui->lbl_selection->text())));
        return;
    }
    QString file, cmd;
    QStringList args;
    QProcess *proc = new QProcess(this);
    QProgressDialog *dlg = new QProgressDialog("Normalisation", "Cancel",0,0);
    dlg->setModal(Qt::WindowModal);
    file = QString("%1/%2.mp3").arg(currentDir, ui->lbl_selection->text());
    cmd = "lame";
    args.append("--scale");
    args.append("2");
    args.append(file);
    args.append(tmpFile);
    proc->start(cmd, args);
    connect(proc, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(procEnd(int)));
//    proc->waitForFinished(); /// Including this leaves blank previous dialogues. 
    dlg->exec();
    connect(proc, SIGNAL(finished(int)), dlg, SLOT(close())); /// These don't seem to work
    connect(dlg, SIGNAL(finished(int)), proc, SLOT(kill()));   /// ditto
}
 
void MP3collection::procEnd(int i)
{
//It would be nice to close the dialogue here but it doesn't know about [I]dlg[/I] of course. 
    qDebug()<<i;
//    close();
}

The program runs and the process works as expected. I cannot stop the process and the dialogue remains after the process has finished requiring the cancel button.

Any advice would be much appreciated.
Thanks in advance
Graham