[SilverKiller]

Make :

pawn Код:

new DM[MAX_PLAYERS]; // At Top

In OnPlayerConnect :

pawn Код:

DM[playerid] = 0;

And in your command :

pawn Код:

DM[playerid] = 1;

Then in the other commands where we will block the command if he is in the DM :

pawn Код:

if(DM[playerid] == 1) return SendClientMessage(playerid, -1, "You can't use this command in a DeathMatch!");

And in /exitdm add :

pawn Код:

DM[playerid] = 0;

Hope i helped.

EDIT : Too late.