[Flori]

Use a timer for this

pawn Code:

new Advert[MAX_PLAYERS];

CMD:ad(playerid, param[]) 
{ 
    if(Advert[playerid] ==1)return SendClientMessage(playerid,0x33AA33AA,"You're just allowed to advert each 30 seconds");
    { 
    SetTimerEx("AdvertWait",30000,false,"i",playerid);
    Advert[playerid] = 1;
//Make here the advert or whatever
    return 1;
}

forward AdvertWait(playerid);
public AdvertWait(playerid)
{
    Advert[playerid] = 0;
    SendClientMessage(playerid,0x33AA33AA,"You're now again allowed to advertise your car.");
    return 1;
}