Can you clarify "send commands from VA to chat"? You should be able to control either one as you can any Windows application: By clicking the GUI and sending keystrokes.
If you're looking to for something like "Ban SomeUser for 10 minutes" by name, that's not going to work simply because the speech engine can't recognise something like a nickname freeform, and dynamic command names aren't implemented.
Even without that restriction, you'd have to get the user list into VoiceAttack so it knows where to click.
You could do "Ban the fifth user in the list for 10 minutes", where you refer to the relative position of a user in the userlist, in which case you can capture the coordinates for them relative to the window.