TIdMessage ... nested parts ?

My objective is to send an email  using  TIdMessage, TIdText,
TIdAttachmentFile
   consisting of
         multipart/alternative  parts:
              one with plain text,
              second with same content in html,
PLUS
     an attachment which is itself an html document with embedded references
          to two jpeg images which should also be delivered as part of the
overall message.

1) Is it true that I need nested parts .... something like :
            Message    (multipart/mixed )
                 -  Part 1         (multipart/alternative)
                                1.1     plain text
                                1.2     html
                 - Part 2       attachments
                               2.1   html attachment
                               2.2     jpeg1
                               2.3     jpeg2

2)  If so, what is general syntax to create this nested structure with  Indy
10    (with Delphi 7)

Thanks for suggestions.