Oracle WebServer (PL/SQL & Unix)

Does anyone know whether you can execute a UNIX shell script inside a PL/SQL package procedure? What I'm trying to do is create a document check-in form. The form basically contains 3 fields: 1) name of the document, 2) source directory (where doc currently resides), & 3) destination directory (where doc is to be placed). Once the user fills out the form on the Web, they click on the 'Check-in' button. It would then run my Unix shell script which is basically just a 'cp' command. Here's part of my procedure. Currently I show another procedure to be executed (checkinAction) when the button is clicked...this is where I'm stumped. How do I call a Unix script inside this Oracle procedure? Appreciate any suggestions.

 htp.formOpen ('pdm.checkinAction');
 htp.formText ('doc_nbr');
 htp.formText ('src_dir');
 htp.formText ('des_dir');
 htp.formSubmit (null,'Check-in');