Anyways, this post is a reference point to myself and fellow googlers who get "Could not execute command" error while trying to tweak xmobar to have a volume indicator or any other command running using "Run Com" in xmobarrc.
Long story short, it's possible that your Run Com references "~" as part of the path or anything else that is expected to be expanded. Solution:
Run Com "/bin/bash" ["-c", "~/path/to/your/script"]
... or... just expand "~" to /home/ahtik/
The longer uncut story: a change in xmobar (dated 2013) made the command running more secure by switching from runInteractiveCommand to runInteractivePRocess. See #127 at Github
Cheers! Stay strong.