SetPreviousButtonHidden
wizard->SetPreviousButtonHidden(true);
wizard->SetPreviousButtonHidden(false);
wizard->SetPreviousButtonHidden(false);
wizard->SetPreviousButtonHidden(false);
fWizardView->SetPreviousButtonHidden(!fHasInstallableItems);
SetPreviousButtonHidden(true);
SetPreviousButtonHidden(false);
virtual void SetPreviousButtonHidden(bool hide);