Due to limitations of the Dreamweaver Insert Record Server Behavior, the uplaoded file name can not be retuned at insert time.
to accomplish this, you will need to use the DataAssist insert record server behavior instead:
The problem is that the Dreamweavver insert record behavior will only allow you to get information from form elements.
The server file name is not created until the file is uploaded to the server. The server file name is only available at run time and cannot be assigned to form since it is created after the form submits.
The DataAssist insert record behavior will allow yo to get information from any server variable listed in the bindings panel, including the Upload Files -> Server File Name