That worked, to a point. First, my ES300h doesn't let me enter phone numbers directly--they have to be entered into my phone as contacts, and then transferred to the car. Following the directions in the article you pointed me to, it seems that a simple pause ("p") is not long enough between the VM access number and the code. A wait ("w") stops the process and waits for further input. (And for some reason, stringing two p's together gets transformed into a w.)
The result is this: The car will dial the VM access number and then wait for further input. On the display screen, I can click on the "0-9" button, which brings up the number pad. Ordinarily, you can't enter numbers while you're moving, but because the code is already programmed into the contact, that code already populates the screen, so I just press the "send" (or "send numbers", or something like that) button, and the code is sent.
So, your suggestion helped. But it requires that extra step of actually sending the passcode.
If anyone knows of a way to make a longer pause without transforming it into a wait, I'd appreciate knowing.
Thanks!
(BTW, I see you have a bike. I have a 2006 Ultra Classic Electra Glide...)