I've set my factory alarm off by accident a couple of time (opened the door without disarming) and I've been able to just put the key in the ignition and either turn it to run or start the VX and the alarm has stopped. Maybe give that a try? Put the new battery in then start the VX while the alarm is going and it should stop.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless