[SickAttack]

pawn Code:

#define MAX_DIALOGS_USED 10
new bool:DialogUsed[MAX_PLAYERS][MAX_DIALOGS_USED];

// Disalow a player to use the dialog 5 again:
DialogUsed[playerid][5] = true;

// Checking:
if(DialogUsed[playerid][5] == true) SendClientMessage(playerid, 0xFFFFFFFF, "You can't use the dialog 5 again!")