runas log off vbs script that calls a batch file

Hi. I want to run a log off script that will enable the automatic updates service in xp. The users do not have admin rights and we cant make them members of the power users group.

I have a vbs script that does a runas on batch file with admin credentials. But now and then when logging off, a command window still prompts asking for the password. When running the vbs file manually, it works every time.

Please see script below

Option Explicit

Const USER = "domain\user"
Const PASS = "password"
Const WSNAME_COMMANDLINE = "\\domain\SYSVOL\domain\scripts\Enable AND Start Update Service.bat"

Dim fso         : Set fso = CreateObject("Scripting.FileSystemObject")
Dim WSHShell    : Set WshShell = CreateObject("WScript.Shell")
Dim WshNetwork  : Set WshNetwork = CreateObject("WScript.Network")
Dim oDic        : Set oDic = CreateObject("Scripting.Dictionary")
Dim objArgs     : Set objArgs = WScript.Arguments
Dim oProcessEnv : Set oProcessEnv = WshShell.Environment("PROCESS")

Dim sPathToRunAs, iReturnCode

sPathToRunAs = oProcessEnv("SystemRoot")&"\System32\runas.exe"
''msgbox sPathtorunas

if Not fso.FileExists(sPathToRunAs) Then : WScript.Quit(1) 'Can't find RunAs

'''msgbox "runas /user:" & USER & " " & CHR(34) & WSNAME_COMMANDLINE & CHR(34)
iReturnCode=WshShell.Run("runas /user:" & USER & " " & CHR(34) & WSNAME_COMMANDLINE & CHR(34), 2, FALSE)

Wscript.Sleep 30000                ' Time for window to open.
WshShell.AppActivate(sPathToRunAs)' Activate the Window
Wscript.Sleep 30000
WSHShell.SendKeys PASS & "~"      ' Send the password
Wscript.Sleep 30000

I have tried changing the wscript.sleep value even to 10000 but still no joy

If anyone has any ideas, please let me know