Sounds like the simplest solution would be to enable file auditing on that directory and use the Windows Event Log Monitor to search for the specific event that's written to the event log when a file is created in that directory and alert when that event isn't found after "x" period of time. The templates below are another possible option. If neither of these options pan out you might find someone capable of helping you write a SAM script that would do this by posting in the Script Lab.