forward isPlayerInArea();
   public isPlayerInArea()
   {
       new Float:X, Float:Y, Float:Z; //We use this to store player position
       for(new i=0; i < MAX_PLAYERS; i++) //This line defines a name for all player, the name is "i"
       {
           GetPlayerPos(i, X, Y, Z); //Here we are storing the player position on the variables X, Y, and Z defined previously
           if (X <= -1899 && X >= -1874 && Y <= 384 && Y >= 338)
           /* This line is the important one!. Here, is where you change those numbers, by the ones
           you get from the /pos command. As you can see, those coordinates, are only the X and Y ones, the Z
           doesnt matter*/
           {
               SetPlayerHealth(i, -999999.9); //This will ensure, that our player gets killed if he tries to enter
           }
       }
   }

SetTimer("isPlayerInArea", 1000, 1);

public isPlayerInArea()
   {
       new Float:X, Float:Y, Float:Z; //We use this to store player position
       for(new i=0; i < MAX_PLAYERS; i++) //This line defines a name for all player, the name is "i"
       {
           GetPlayerPos(i, X, Y, Z); //Here we are storing the player position on the variables X, Y, and Z defined previously
           if (X <= <here> && X >= <here> && Y <= <here> && Y >= <here>)
           /* This line is the important one!. Here, is where you change those numbers, by the ones
           you get from the /pos command. As you can see, those coordinates, are only the X and Y ones, the Z
           doesnt matter*/
           {
               SetPlayerHealth(i, -999999.9); //This will ensure, that our player gets killed if he tries to enter
           }
       }
   }