To schedule using exchange server 2007
you must use a batch file that is scheduled with task manager
the batch file should run GetEvent.psl script, e.g.
PowerShell.exe -PSConsoleFile "C:\program files\microsoft\exchange server\bin\ExShell.psc1" -Command ". 'c:\program files\microsoft\exchange server\scripts\GetEvent.psl' -Log "Application -ID "1022""