once you get the timer part (30 minutes thing) this will ask if you want to shut down .. note. Shows Dos window .. and BTW if you answer yes it will shutdown right away.

Code:
Option Explicit

Dim objShell, Question, Shutdown
Question = MsgBox("Turn Off Computer?", vbYesNo, "Shutdown")

If Question = vbYes Then
    Shutdown = "shutdown -s -t 00"
    Set objShell = CreateObject("WScript.Shell")
    objShell.Run "cmd"
    Wscript.Sleep 100
    objShell.SendKeys Shutdown
    objShell.SendKeys "{ENTER}"
End if