Does already exists a script which is watching a directory and when a change occures follow with a special action ?

Take a look at various "file-watch" job templates (File/New/Job From Template menu)

Also check available examples in the on-line help. For instance, open DirWaitForUpdate topic and click the Examples button on the help system toolbar

: Does already exists a script which is watching a directory and when a change
: occures follow with a special action ?