Signing selected .exe file(s) with signtool.exe?

I am trying to create a button which signs the selected .exe file (or better multiple selected files?) with my signtool.exe. This works fine from the command line but not with the button I created:

cd "C:\Program Files (x86)\Windows Kits\8.1\bin\x64"
@async:"C:\Program Files (x86)\Windows Kits\8.1\bin\x64\signtool.exe" /a "{filepath}"

{filepath} is quoted automatically, if the path contains spaces (unless you add @nofilenamequoting), so adding explicit quotes around it may be resulting in two sets of quotes.

The signtool documentation also says you are missing the sign argument in your command. Are you sure it's exactly the same as what you're running at the command line?

Thank you, Leo, I am such a fool, I forgot the sign command. Now, of course, it works.

But how can I do it with multiple selected files? (I assume that multiple selected files could/would be passed sequentially to the signtool.exe)?

What you have should already do that.

Thank you, Leo!