I get the funny feeling that somewhere there's an assumption that isn't making it's way into the open.   If you run an SSIS job via the SQL Agent, you are probably going to have that job executing on the server on which SSIS is installed, and then, when the SSIS package runs, it's going to try and run that script locally to that server, so if that server doesn't have Excel installed on it, then it's not going to work.   It might not fail, either.   If you develop on your laptop or desktop, having Excel installed on that desktop or laptop is not going to help at all under those circumstances.   Hopefully, that at least clears up what Phil was trying to say.

If you run the SSIS package locally, it will only run correctly if you have a local instance of SSIS installed, and Excel.   Both would be required wherever that package runs.   Does that help at all?