Modifying 'objAction=ReserveDoc' Dialog for special subtype

NGIT_Austria_(x-ngitat_-_(deleted))

I have implemented a new subtype (everything works fine). Now I have to *modify* the dialog (objAction=ReserveDoc) for my subtype (present some additional informations). How do I do this:which orphans?where to register my subtype?thanx in advance for any hints