Excel VB.net Add-in Error sending Outlook email

Hi

I am using the following code to send an email via Outlook from my Excel VB.net add-in.
I get an error at the line marked ERROR HERE. The error is "Process aborted...."
What am I doing wrong?

Imports Microsoft.Office.Interop.Outlook

Module modEmail

    Sub oSendEmail(ByVal oTo As String, ByVal oCc As String, ByVal oSubject As String, ByVal oBody As String, ByVal oAttachment As String)

        Try


            ' Create an Outlook application.
            Dim oOutApp As Microsoft.Office.Interop.Outlook.Application
            oOutApp = New Microsoft.Office.Interop.Outlook.Application

            ' Create a new MailItem.
            Dim oMsg As Microsoft.Office.Interop.Outlook.MailItem
            oMsg = oOutApp.CreateItem(Microsoft.Office.Interop.Outlook.OlItemType.olMailItem)

            oMsg.Subject = oSubject
            oMsg.Body = oBody
            oMsg.To = oTo
            oMsg.CC = oCc

            ' Add an attachment
            Dim sSource As String = oAttachment 'eg "C:\Temp\Hello.txt"
    '++++++++++++++++
            Dim sBodyLen As String = oMsg.Body.Length ''ERROR HERE
            Dim oAttachs As Microsoft.Office.Interop.Outlook.Attachments = oMsg.Attachments
            Dim oAttach As Microsoft.Office.Interop.Outlook.Attachment
            If oAttachment <> Nothing And oAttachment <> "" And System.IO.File.Exists(oAttachment) = True Then
                oAttach = oAttachs.Add(sSource, , sBodyLen + 1)
                'oAttach = oAttachs.Add(sSource, , sBodyLen + 1, sDisplayName)
            End If

            ' Send
            oMsg.Send()
            ' Clean up
            oOutApp = Nothing
            oMsg = Nothing
            oAttach = Nothing
            oAttachs = Nothing
        Catch
            MsgBox("An error occurred in trying to send an email! " & Err.Description)
        End Try

    End Sub