I was actaully able to piece the following together and get this to work.
Dim _item As Outlook.MailItem = Globals.ThisAddIn.Application.ActiveInspector().CurrentItem
Dim objMsg As Outlook.MailItem
'Get the currently open message'
objMsg = Globals.ThisAddIn.Application.ActiveInspector().CurrentItem
objMsg.Subject = objMsg.Subject & "(Secure) "
'Destroy the object to avoid memory leaks'
objMsg.Send()
objMsg = Nothing