I don't think so. If there was, it would have been added. I don't think there's a "close" command that can be sent to any drives, since doing so can be risky (fingers not out of the way, disc not fully in the tray, et cetera).
Whoops, I'm wrong. Apparently there is such a command, but not all drives actually have it. Microsoft wouldn't put the command in since it wouldn't always work then.
There's a Linux command "eject" which apparently has a command line option that issues the close command. But I've never heard of one for Windows.