2000 express brake light question

i have a 200 express and need some info. id like a swith to put inline to the brake lights. i know theyre not wired in a series, so either each has its own ground, or im looking for four wires. i have no schematics, and i think if i break the feed from the fuse it will kill ofther lights (parking, tail lights or whatever else is in the loop.) anyone know where i can catch these wires up sront.even colorrs might help. thanks

i have a 200 express and need some info. id like a swith to put inline to the brake lights. i know theyre not wired in a series, so either each has its own ground, or im looking for four wires. i have no schematics, and i think if i break the feed from the fuse it will kill ofther lights (parking, tail lights or whatever else is in the loop.) anyone know where i can catch these wires up sront.even colorrs might help. thanks

That could be a illegal operation.
Why do you want to do that?