void Wizard::ComputeAndSetSize(wxWizardPage* startPagePtr)
{
    wxSize size = startPagePtr->GetBestSize();
    for(wxWizardPage* pPtr = startPagePtr->GetNext(); pPtr; pPtr = pPtr->GetNext())
    {
        wxSize tmpSize = pPtr->GetBestSize();
        if(tmpSize.GetHeight() > size.GetHeight())
            size.SetHeight(tmpSize.GetHeight());
        if(tmpSize.GetWidth() > size.GetWidth())
            size.SetWidth(tmpSize.GetWidth());
    }
    SetPageSize(size);
}

   size.SetHeight(300);
   size.SetWidth(200);
   wizard->SetPageSize(size);