Below follows a easy script to check if a certainfile becomes to large and if so generate a eventlog entry.
Option Explicit
Dim FSO, File, strSize, strFile, alarmSize, WshShell
' As scheduled scripts dont like arguments tell the script which file to check
strFile="c:\pagefile.sys"
' The size to check against in Megabytes
alarmSize=300

Set FSO = CreateObject("Scripting.FileSystemObject")
Set File = FSO.GetFile("c:\pagefile.sys")
strSize = File.Size\1024\1024
'Wscript.Echo "Filesize : " & File.Name & " is " & strSize &"Mb. Alarmsize set to" & alarmSize & " Mb."
If strSize > alarmSize Then
	'Wscript.Echo "Filesize Varning: " & File.Name & " is larger then " & alarmSize &" Mb"
	Set WshShell = CreateObject("WScript.Shell")
	WshShell.LogEvent 4, "Filesize Varning: " & File.Name& " is larger then " & alarmSize &" Mb"
	Set WshShell = nothing
End If
Set File = Nothing
Set FSO = Nothing
Wscript.Quit(1)