How to move extra checkbox to the bottom left corner in QFileDialog window in QT3

I have problem with moving checkbox from middle to the left:

 #include <qfiledialog.h>
    #include <qcheckbox.h>
    class FileDialog : public QFileDialog
    {
    public:
    QCheckBox* checkbox
    FileDialog() : QFileDialog(0)
    {
        checkbox = new QCheckBox(this);
        checkbox->setText("checkbox");
        addWidgets( 0, checkbox, 0 );
    }
    };

Looks like it: enter image description here

I need to move it like this(better option): enter image description here

or like this: enter image description here

I can't use this method:

#include <qcheckbox.h>
#include <qlabel.h>
#include <qlayout.h>
class CheckBox : public QLabel
{
  QCheckBox* checkbox;
public:
  CheckBox(QWidget * parent) : QLabel(parent)
  {
    QGridLayout * box = new QGridLayout(this);
    checkbox = new QCheckBox(this);
    checkbox->setText("checkbox");
    box->addWidget(checkbox, 0, 0, Qt::AlignLeft);
  }
  void paintEvent ( QPaintEvent * ){}
};



class FileDialog : public QFileDialog
{
public:
  FileDialog() : QFileDialog(0)
  {
    addWidgets(new CheckBox(this), 0, 0);
  }
};

I need other way to solve this problem. Somebody can help me? :)