Customize button to be enabled only when file type is selected

I have created a new button that will mount an .ISO file as a virtual CD. The button always shows enabled.
Is there a way to enable it ONLY when I have selected an .ISO file? This program has so many capabilities
that i'm sure it's possible... but I can't find it.

Thanks...

You can use @disablenosel:files so the button is only enabled when files are selected, but can't narrow it down by file type.

There are various ways to make sure the button will only run on .iso files if it is clicked with a mixture or other file types selected, if needed.

Alternatively, putting the mount command on the ISO filetype's context menu might be preferable.