So what part are you having problems with? I'm assuming by your screen shot that you have the post.asp additions working.
As for the post_info.asp
search for this
txtMessage = ChkString(Request.Form("Message"),"message")
txtSubject = ChkString(Request.Form("Subject"),"SQLString")
and replace with
'#### Steve D.'s Event Add On ####
dim EventMessage
EventMessage = "Location: " & Request.Form("event_Location") & vbNewLine
EventMessage = EventMessage & "Time: " & Request.Form("event_StartTime") & " - " & Request.Form("event_EndTime") & vbNewLine
EventMessage = EventMessage & "Cost: " & Request.Form("event_Cost") & vbNewLine
EventMessage = EventMessage & "Website: " & Request.Form("event_Website") & vbNewLine
txtMessage = ChkString(EventMessage & vbNewLine & Request.Form("Message"),"message")
' #####################################################
txtSubject = ChkString(Request.Form("Subject"),"SQLString")
That should work, or need some slight tweaking