You will need a few extra lines for that:

Sub SendOnMessage(olItem As Outlook.MailItem)
Dim olOutMail As Outlook.MailItem
Dim olInsp As Outlook.Inspector
Dim wdDoc As Object
Dim oRng As Object
    Set olOutMail = olItem.Forward
    With olOutMail
        .To = "someone@somewhere.com"
        .Subject = "HC"
        .Display
        Set olInsp = .GetInspector
        Set wdDoc = olInsp.WordEditor
        Set oRng = wdDoc.Range(0, 0)
        oRng.Text = "Message was sent from: " & olItem.SenderEmailAddress
        .sEnd
    End With
lbl_Exit:
    Exit Sub
End Sub