forward ChangeHostname();

new
    gChangeHN;

public OnFilterScriptInit()
{
  SetTimer("ChangeHostname",5000,1);
  return 1;
}

public ChangeHostname()
{
    switch (gChangeHN)
    {
        case 0: SendRconCommand("hostname My server name 1");
        case 1: SendRconCommand("hostname My server name 2");
        case 2: SendRconCommand("hostname My server name 3");
    }
    if (gChangeHN == 3)
    {
        gChangeHN = 0;
    }
    else
    {
        gChangeHN++;
    }
}