Create button with relative path

[whiskytechfred]

Hello,
I'd like to customize a button to launch an app using a relative path.  This button would launch an app relative to the MC path.
I looked at external commands and I don't seem to be able to use %~d0 or the like.
I also looked at Multi-Script but the path commands seem to be related to the source or target panels.
Is there a way to achieve what I'm looking for?
Thanks in advance,
Fred

[whiskytechfred]

I found I can use something like:
${mcpath}\..\..\app.exe
and that works!

Sorry for the useless entry.
Fred