Setting Player CVar on join

I’m just getting into GMod Lua coding, and I’ll admit I’m not too great with it yet. I hope this hasn’t just been covered elsewhere, but using gmsv_gatekeeper I want to validate a user based on SteamID (comparing it to a list of specific IDs), and if it’s in the list, set their rcon_password to whatever the server’s current rcon_password is. This is of course serverside-only, and it’s basically meant to be a way to streamline rcon access for administrators.

So, apologies if I missed this while looking for anything similar, but if anyone could give me some help or direction for where to find this out I’d really appreciate it!

All commands concerning rcon are blocked.

Tidies that question up neatly then. Thanks for your time.