[CmZxC]

Do you mean once he's attaching it or if he has it already attached?

PHP код:

public OnTrailerUpdate(playerid, vehicleid)
{
    new id_veh = GetPlayerVehicleID(playerid);
    if(GetVehicleModel(id_veh) == 403 && GetVehicleTrailer(id_veh) == 584)
    {
        // he done did it
    }
    return 1;
}