What you describe can be done with
nicklist.dll, however I still recommend nicklust because it's easier in that it takes care of nickname updating and auto-resizing.
This code will get you started:
- On me:*:join:#:{
dll nicklust.dll Mark # > noheader
dll nicklust.dll SetIcon # op > 20, $+ $mircexe
}
Both DLL packs include comprehensive tutorials.