[(Jeff)]

pawn Код:

new IsAnyOneInDM[MAX_PLAYERS];

then:

pawn Код:

if (strcmp("/joinDM", cmdtext, true, 10) == 0)
    {
    if(IsAnyOneInDM[playerid] == 0;
        {
         IsAnyOneInDM[playerid] == 1;
         SendClientMessageToAll(color,"DM Has Been Started Use /joinDM");
    }
    else
    {
     SendClientMessage(playerid, color,"DM Has Already Been Started Use /joinDM");
        }
        return 1;
    }

i did that in about 4 minutes xD I'm not that it works 100%