You can’t edit timers through the chat, but as @abomination said, you can use an alias and edit the message in the alias command, but that’s time consuming and it doesn’t address the changing time component (even tho’ if that’s what you’re after, you should consider using commands instead of timers), so here’s another solution you could use and adapt to your case:
I’d personally use a Pastebin instead of the Quote API, but that works.