Yes but this would not be a regular S/PDIF cable. One end of the cable would need to have a 3.5MM fixture, while the other end would need to have either optical or C0-Axial (those are digital connections.) I have seen the S/PDIF cable with one end of it being a 3.5MM connection but the other end is a left/right RCA composite connection (which is NOT digital, it's analog.)
So S/PDIF is digital, in order to keep it all digital whatever your plugging it into (from the notebook to an external sound system) has to be going into either one of two ports (optical or Co-Axial.) If not, your wasting your time connecting it via the S/PDIF port on the notebook.
That's why I'm confused (with regards on finding the cable, I can't find them anywhere.)