"togglevplock" works at the command prompt, but not defined as TVA.
Can't answer your "real" question, but just FYI. "TOGGLEVPLOCK" is a lisp function, not a command. So it won't run from
(command "togglevplock" ....)
It amy work if called as a routine by
(defun c:tva () (togglevplock))
but not knowing anything about the code, I'm just guessing.