I'm not sure how you're trying to send the "Set Level" command, but it sounds like you have a switch, and that command is generally only available on dimmers (things they let you set a level--brightness). It's also unlikely to work for this purpose in any case (though a custom driver could if it were written that way).
Assuming your driver doesn't provide any options, since you know the parameter number and have the manual handy (you'll also need the parameter size and desired value), I'd use the Basic Z-Wave Tool to do this. Just install that driver, temporarily switch to it, make the change, then switch back:
