Sending a text message in Outlook with .net

This is the first time I've asked a question on here, so apologies if anything is unclear.

I'm using a .net application to read and send email with Outlook. This is the done with the Outlook object library with the code below:

Private Sub SendEmail(ByVal Message As String, ByVal EmailAddress As String)
    Dim objOutlook As Object
    Dim objOutlookMsg As Object
    objOutlook = CreateObject("Outlook.Application")
    objOutlookMsg = objOutlook.CreateItem(0)
        With objOutlookMsg
            .To = EmailAddress
            .Subject = "Subject"
            .Body = Message
            .Send()
        End With
        objOutlookMsg = Nothing
        objOutlook = Nothing
End Sub

Outlook 2010 supports sending text messages. I've set this up and I can send a text message manually from the Outlook application. My question is how do I adapt the code above to send a text message instead of an email? The Createitem array doesn't have a "text message" object and I couldn't find any examples elsewhere.