The short answer is Yes. The long answer is painful. There aren't any great classes exposed to manipulate rich text items in Notes. However a few that you can research are the NotesRichTextStyle, NotesRichTextParagraphStyle, and NotesRichTextTable to name a few. These classes help you define some rich text elements and add them programmatically to your rich text field.
Another approach, since you're sending email, is to use the NotesMIMEEntity classes and build the email using HTML (way way easier). Here's some sample code:
Set s = New NotesSession
Dim docMail As NotesDocument
Dim body As NotesMIMEEntity
Dim stream As NotesStream
Set db = s.CurrentDatabase
s.ConvertMIME = False ' Do not convert MIME to rich text
'Create email to be sent
Set docMail = db.CreateDocument
With docMail
.SendTo = SEND TO ADDRESS
.From = FROM ADDRESS
.Principal = FROM ADDRESS
.ReplyTo = REPLY TO ADDRESS
.Subject = SUBJECT
.Form = "Memo"
End With
Set stream = s.CreateStream
Set body = docMail.CreateMIMEEntity
Call stream.WriteText ("YOUR HTML CODE GOES HERE")
'ENC_IDENTITY_8BIT used because of technote found on notes.net
'http://www-10.lotus.com/ldd/nd6forum.nsf/55c38d716d632d9b8525689b005ba1c0/aeedaf28e47546ad85256f6a000a4b48?OpenDocument
Call body.SetContentFromText (stream, "text/html;charset=iso-8859-1",ENC_IDENTITY_8BIT)
Call docMail.Send(False)
Set docMail = Nothing
Set body = Nothing
Set stream = Nothing
s.ConvertMIME = True ' Restore conversion
Essentially you'll need to turn the ConvertMIME setting off in the NotesSession. Then create a new document, set the mail properties, etc. That part is already in your VBA code. Next, create the MIMEEntity and a stream to hold your HTML text. Finally call the SetContentFromText method on your MIMEEntity object. Then send your email. Note the last call is to turn the ConvertMIME feature back on for the NotesSession.
I'm not sure if this will all work via COM, but it does work well in LotusScript agents in Notes.
I hope this helps!