Since you're using FM12 take a look at the new script step:
Insert From URL()
With this step it's possible to insert a file using the 'file' protocol, which means if you have the full path to the file on the local FMS it can do what you're looking for. See http://www.filemaker.com/12help/html/scripts_ref1.36.46.html for further details.
That'll do it. Took me a bit to get the format correct: file:///C:/[PATH]
Thank you so much!