A member of the dope very kindly gave me the following code to reply to a plain-text email in html.  Unfortunately I forget who it was.  But I’ve already thanked them 
Anyway. This code does a ‘reply’ email. In other words it replies to the first person in the ‘from’ field.
Option Explicit
Public Sub ReplyToPlainTextWithHTML()
   Dim HTMLReplyMail As Outlook.MailItem
 
   If Application.ActiveExplorer.Selection.Count Then
 
      If TypeOf Application.ActiveExplorer.Selection(1) Is Outlook.MailItem Then
 
         Set HTMLReplyMail = Application.CreateItem(olMailItem)
 
         HTMLReplyMail.To = Application.ActiveExplorer.Selection(1).SenderEmailAddress
         HTMLReplyMail.BodyFormat = olFormatHTML
         HTMLReplyMail.Subject = "Re: " & Application.ActiveExplorer.Selection(1).Subject
 
         Dim SigString As String
         SigString = "C:\Documents and Settings\" & Environ("username") & _
                                     "\Application Data\Microsoft\Signatures\compact.htm"
         Dim mailSig As String
         If Dir(SigString) <> "" Then
            mailSig = GetBoiler(SigString)
         Else
            mailSig = ""
         End If
          HTMLReplyMail.HTMLBody = "<br><br>" & mailSig & "<br>" & _
                                 "-----Original Message-----" & "<br>" & _
                                 "From: " & Application.ActiveExplorer.Selection(1).SenderName & "<br>" & _
                                 "Sent: " & Application.ActiveExplorer.Selection(1).SentOn & "<br>" & _
                                 "To: " & Application.ActiveExplorer.Selection(1).To & "<br>" & _
                                 "cc: " & Application.ActiveExplorer.Selection(1).CC & "<br>" & _
                                 "Subject: " & Application.ActiveExplorer.Selection(1).Subject & "<br>" & _
                                  Application.ActiveExplorer.Selection(1).HTMLBody
 
        HTMLReplyMail.Display
 
      End If
 
   End If
End Sub
Function GetBoiler(ByVal sFile As String) As String
'Dick Kusleika
    Dim fso As Object
    Dim ts As Object
    Set fso = CreateObject("Scripting.FileSystemObject")
    Set ts = fso.GetFile(sFile).OpenAsTextStream(1, -2)
    GetBoiler = ts.readall
    ts.Close
End Function
So my question is, how would I go about changing this code so that it does ‘reply to all’ instead of just ‘reply’?