[Randy More]

Define this globally, anywhere after the includes lines:

pawn Код:

new IsInIsland[MAX_PLAYERS];

And make a specific value set for the variable if the player in the island, and to be changed when leaving.

pawn Код:

CMD:islanddm(playerid, params[])
{
    if(IsInIsland[playerid]) return SendClientMessage(playerid, COLOR_RED,"You are already at the island!");
    new string[128], pName[MAX_PLAYER_NAME];
    GetPlayerName(playerid, pName, MAX_PLAYER_NAME);
    SetTimerEx("Unfreeze", 2000, 0, "d", playerid);
    GameTextForPlayer(playerid,"~g~Waiting for the Objects to load",2000,3);
    format(string, sizeof(string), "{FF0000}(/islanddm) {FFFF00}Player {FF0000}%s {FFFF00}has Teleported to {FF0000}Island DeathMatch",pName);
    SendClientMessageToAll(playerid, string);
    new Random = random(sizeof(RandomSpawnIslandDM));
    SetPlayerPos(playerid, RandomSpawnIslandDM[Random][0], RandomSpawnIslandDM[Random][1], RandomSpawnIslandDM[Random][2]);
    IsInIsland[playerid] = 1;
}

CMD:leavedm(playerid, params[])
{
    if(!IsInIsland[playerid]) return SendClientMessage(playerid, COLOR_RED,"You are not at the island - /islanddm to join!");
    new Random = random(sizeof(RandomSpawnLEAVEDM));
    SetPlayerPos(playerid, RandomSpawnLEAVEDM[Random][0], RandomSpawnLEAVEDM[Random][1], RandomSpawnLEAVEDM[Random][2]); // Place the X Y Z of the position where they player will be when they type this command
    SendClientMessage(playerid, COLOR_RED, "You have left the Deathmatch Area");
    IsInIsland[playerid] = 1;
    return 1;
}

And for the checking for the commands you want to use when only at the island make it like the example stated when joining.