QT3 How to add checkbox to QFileDialog window

I have problem with adding extra checkbox to QFileDialog window. Im talking about the same window which is opened during using QFileDialog::getSaveFileName. I know how to do this in QT5, i need to make a subclass and set option QFileDialog::DontUseNativeDialog. But how can i do this in QT3? because there i don't have QFileDialog::DontUseNativeDialog. In QT3 there is a fewer methods to choose. Is there similar method or maybe completely different to add this checkbox?