[Basicz]

variables, obviously

pawn Код:

new
    bool: sendMsg[ MAX_PLAYERS ]
;

public OnPlayerConnect( playerid )
{
    sendMsg[ playerid ] = true;

    return 1;
}

// ...

for(new i = 0; i < sizeof(BizInfo); i++)
            {
                if(!IsPlayerInRangeOfPoint(playerid,25.0,822.1263,2.8237,1004.1797))
                {
                    if ( sendMsg[ playerid ] ) {
                    SendClientMessage(playerid, COLOR_WHITE, "You are not in an advertising agency or at the desk");
                    sendMsg[ playerid ] = false;
                    } }

EDIT: wtf? loop?
Why do you even need that loop?

pawn Код:

if ( !IsPlayerInRangeOfPoint( ... ) )
    return SendClientMessage( playerid, COLOR_WHITE, "You are not in an advertising agency or at the desk." );