You could schedule a job every so many minutes to check for files, but my concern is that the changed file is in the same directory. That will make it difficult.
Now everytime you need to check the file on changes. I don't know the contents of this file and if this is easy to do, otherwise you might create a z_table in which you store data about the file (e.g. name, date/time created + hashtotal ) and check if the contents of the file have been changed by creating a new hash total (FM CALCULATE_HASH_FOR_CHAR) and compare this with the hashtotal in the z_table