number to dollars

string InsertCommas(int num)
{
    string number,digit;
    int i = 0;
    do {
        if((i > 0) && (!(i % 3))) {
            number= "," + number;
        }
        digit = (num % 10) + '0';
        number= digit + number;
        num /= 10;
        i++;
    }
    while((num) || (i < 1));
    return number;
}