where is the relay for the horn in my bmw 323 e46?

the horn in my bmw 323 e46 doesnt work. i have checked the fuses and all ok. i bought a haynes manual which tells me the relay code but once i dismantled the glovebox (where it tells me the relay is), i could only find 4 relays, none of which is the one im looking for.
has anyone got any ideas where the relay could be?
many thanks