Quick key to open a program and open file selected

Sorry if this is an easy one. I'd like to fix it so I can select an image file, then hit a quick key to use my program to open the image. I would use dopus but this is a Maya .iff file (not amiga) and opus doesn't support it. I'm using the bundled utility "fcheck" to open my .iff files. I've already tested in a run command line that typing fcheck image.iff will open the requested image, I'm just not sure how to program opus to send the command fcheck -selected image- to windows command line.

TIA!

It's just

fcheck {filepath$}

See the manual, or John's tutorial on external command codes in the Downloads section, for info on codes like {filepath$}.