You're having problems hooking your own messages or what ?
message_* can't be hooked, emessage_* can.
If other plugins use that you can't hook them unless they're emessage_*.
Ham_TakeDamage would be the best way, that triggers whenever player takes real damage.
Hooking health msg could also work and you can get the dmg type from an offset (I think).
If that's not it, then I don't really understand what you want.