I'm not sure were to place this, but here goes.
I created a script that would take an input file, process it and write an output file. It's very simple and I will paste it below:
echo Enter full input file name
echo Enter full output file name
ffmpeg -i "$I" -vn -f wav "$O"
It works from the current directory. But I wanted to be able to call it from a button on my upper panel. I created a link and dragged it to the panel. When I click on it I get this error: