Here is something similar to what you asked. It doesn't intercept !levlist command from chat but instead it will intercept the /levlist console command. Adding the code into a levlist.lua file in the server silent folder. Add the file name in lua_modules like this: set lua_modules "levlist.lua". Once the server starts it will load the Lua modules. You can add many modules into the lua_modules string.
-- function body taken from the rules.lua from N!trox
function et_ClientCommand(clientNum, command)
command = string.lower(command)
--If a client types "/levlist" in his console
if (command == "levlist") then
et.trap_SendServerCommand(clientNum, "chat \""Level 0 - Guest"^7\n\"")
et.trap_SendServerCommand(clientNum, "chat \""Level 1 - Regular"^7\n\"")
return 1
end
end
I didn't test the above but it is an example how to use Lua. More Lua documentation http://mygamingtalk.com/wiki/index.php/Silent_Mod_Server_Cvar#Lua and more detailed documentation in the server.html which came with the silent download.