У объекта QWizard есть замечательная функция.
void QWizardPage::registerField ( const QString & name, QWidget * widget, const char * property = 0, const char * changedSignal = 0 ) [protected]
Creates a field called name associated with the given property of the given widget. From then on, that property becomes accessible using field() and setField().
Fields are global to the entire wizard and make it easy for any single page to access information stored by another page, without having to put all the logic in QWizard or having the pages know explicitly about each other.
Затем можно обращаться к любому полю через
QVariant QWizard::field ( const QString & name ) const
или
QVariant QWizardPage::field ( const QString & name ) const