function updateTotal(nbplaces) {
    price = parseInt(nbplaces) * 499.95;
    tps   = price * 0.05;
    tvq   = (price+tps) * 0.075;
    price = price + tps + tvq;
    price = price.toFixed(2);

    document.getElementById('frm_subscription').amount.value = price;

    price = price.replace('.',',');
    document.getElementById('total').innerHTML = price;
}

function updateNbSeats(idformation) {
    select_content = '<select id="nbplaces" name="nbplaces" onchange="updateTotal(this.value)">';
    if (array_seats[idformation] > 0) {
        for (n = 1 ; n <= array_seats[idformation] ; n++) {
            select_content += '<option value="'+n+'">'+n+'</option>';
        }
    } else {
        select_content += '<option value="">---</option>';
    }
    select_content += '</select>';

    document.getElementById('places').innerHTML = select_content;
    updateTotal(1);
}