Dim WshShell, WshEnv
Set WshShell = WScript.CreateObject("WScript.Shell")
Set WshEnv = WshShell.Environment("Process")
WshShell.Run Chr(34) & WshEnv("ProgramFiles") & "\Microsoft Security Essentials\MpCmdRun.exe" & Chr(34) & " -SignatureUpdate",0,False
Set WshEnv = Nothing
Set WshShell = Nothing