Just copy and paste this code into a text file and rename the extension to .vbs.
Code:
Call WaitRoutine()
Sub WaitRoutine()
Dim intWaitedTime
Dim intMinsToWait : intMinsToWait = -1
Dim objshell
set objShell = CreateObject("WScript.Shell")
strAnswer = InputBox("How many minutes do you wish to wait?","Shutdown Computer")
on error resume next
intMinsToWait = cint(strAnswer)
if (intMinsToWait = -1) or (strAnswer = "") then
msgbox "Shutdown Cancelled.",vbokonly + vbexclamation,"Shutdown Computer"
exit sub
end if
NewDate = DateAdd("N", intMinsToWait, now())
If msgbox("This will shutdown the computer at " & NewDate & ". Continue?", vbquestion + vbyesno,"Shutdown Computer") = vbno then
exit sub
End If
'make script sleep
WScript.Sleep(intMinsToWait * 60 * 1000)
strShutdown = "shutdown -s -t 0 -f -m \\" & "."
objShell.Run strShutdown
Wscript.Quit
End sub