Console script

[Mitch]

You can do this via GSC scripts:

With libcod:
https://killtube.org/showthread.php?3153-callback-RCON

Without libcod:

		level endon("intermission");
setCvar("customcommand1", ""); // can be set via rcon as: /rcon customcommand1 value instead of /rcon set customcommand1 value

for (;;)
{
    if (getCvar("customcommand1") != "") {
        setCvar("customcommand1", "");
        customcommand1(); 
    }

    wait 0.05;
}

customcommand1()
{
}