Is there a way to set the value of one control from the onChange of another control?

[BrendanBerkley]

I have a boolean checkbox and, when it's checked by the user, I'd like it to change the values of controls B, C, and D based on the current value of A.

The docs have a lot of info about setting stuff from outside of controls, but what about inside? Is this possible? If possible, is it a good idea?