try this:
addEventHandler("onPlayerVehicleEnter",root,function(theVehicle) --the vehicle is the first arguement
local vcName = getVehicleName (theVehicle) --source is the player
local mapName = getMapName() -- there's is no arguement needed
if ( mapName == "Arena" or mapName:find ( "Arena" ) and vcName == "NRG-500" or vcName:find ( "NRG-500" )) then
outputChatBox ( "don't Buy NRG-500 in Arena", source, 255, 255, 0, true )
outputChatBox ( "????? ????? ???? ?? ??????? ^_^", source, 255, 255, 0, true )
destroyElement(theVehicle)
end
end)