LOL holy crap this is funny. Okay, here is how you *could* do it on a '98 Corolla, the colors are probably different, if you want the right wire colors let me know.
The stop light switch has a green/white and red/white wire going to it. The horn switch has a geen/red wire that goes to it. Find that horn switch wire, which comes from the horn relay, and splice a spare wire into it. Run your spare wire over and splice that into the red/white wire going to the stop light switch.
Whenever the stop light switch is activated, it will ground the horn relay and turn it on. Removing it is as simple as cutting the spare wire that you used to jumper the two.
For that matter, if the stoplight fuse and the horn relay are near each other, you can run a wire from pin 2 of the horn relay over to either terminal of the stop light fuse, that should also do the trick.
And remember, don't cut the wires, just splice into them. You can use those little "quick splices" like they sell at your local auto parts store.
Worst thing that could happen is one or both of the fuses could blow and the taillights and/or horn wouldn't work.
And don't do this, this is just how you *could* it. And if you do, I wasn't the one who told you how.