The GEL script is running on your PPM server. You have placed the excel document on your local PC. It is not surprising that the GEL script can't read the file, it won't be there.
You will need to contact CA Support for FTP access to your PPM server, to that you can upload the file, and then modify your GEL script to point to it's location (CA Support should also be able to provide the correct path).
Alternative, run the GEL script from your local desktop. There are other Forum Topics raised last week on how to achieve this.