shortcut for \mbox

[Vladimir Smagley]

 \mbox is a very useful feature, unfornutanely there is no shortcut for 
this command.
(Or I couldn't find.)
I have put a line:

\bind "M-m z"                   "math-insert \mbox"

into my .lyx/bind/mykeycuts.bind. Restarted LyX. There is no effect 
whatsoever. What an I doing wrong?
(I'm running RHFC1 Linux on Compag 500MHz machine)
Thanks!

Vladimir