PLAYBACK_EVENT_FULL is just a macro for pfnPlaybackEvent ; so you can hook/call with FM_PlaybackEvent/EngFunc_PlaybackEvent.
All you need to do, is to hook the function at the right time, supercede it, and calling PlayBackEvent for all players except the one you want. First and second params are for flags/invoker. Guess you have to use FEV_HOSTONLY. (hlds_sdk.inc)