Well I solved this issue by looking at Code::Blocks source
Here is the code that is executed when clicking on Help->About, let's asume this code is in MainFrame.cpp
void MainFrame::OnHelpAbout(wxCommandEvent& WXUNUSED(event))
{
dlgAbout dlg(this);
PlaceWindow(&dlg, pdlHead);
dlg.ShowModal();
}
Also the header where dlgAbout is declared have to be manually included the header where it is declared.
Hope this helps in case others face the same problem
~Dr.Optix
PS: i'm not so good at giving explanations :)
EDIT:
so maybe WE can add some option to wxSmith something like child dialogs for a dialog and then based on that list the main dialog include the needed headers. Maybe this is already implemented but i didn't seen it :-