[Konstantinos]

There is an extra bracket. Change to:

pawn Код:

stock ReturnTime(timevariable)
{
    new milliseconds = timevariable, seconds, minutes, string[20];
    while(milliseconds > 9)
    {
        seconds ++;
        milliseconds = milliseconds - 10;
    }
    while(seconds > 59)
    {
        minutes ++;
        seconds = seconds - 60;
    }
    format(string, sizeof(string), "%d:%02d.%03d", minutes, seconds, milliseconds);
    return string;
}

And I'd suggest you to use unix timestamps for the player's time and then you can easily convert the player's time.