Transforming a Countdown timer after it hits zero

Hi folks, I’m making some countdown ads for an event, and usually what I do is made a separate set of ads for when the event is “Live”. The only problem with this is that when the countdown ads get down to zero, the timer starts going up in reverse if you keep watching it (-0:-0:-11:-01 and so forth), and won’t revert to the “live now” ads unless you refresh the page. I was wondering if there is a way to build one master ad combining the elements of both, which will automatically revert to the “live now” status once the timer runs down to zero. Even if it’s something simple like “gotoAndPlay frame #” at a certain time, I’d like to know if it’s possible please?