Upload your JS file to Salesforce.com as a Document. Select the Document, and get the URL in the "Click here to view this file" link. Put this URL in the Script tag's src attribute.
Please make sure that you make this document viewable to all uers that are going to access this S-Control. Also, the user's profile must have Read permissions on Document object. I hope this helps.
Please make sure that you make this document viewable to all uers that are going to access this S-Control. Also, the user's profile must have Read permissions on Document object. I hope this helps.
Thanks.