function subtotal(totalobj, quantityobj, price, min, max) {
    var quantity = quantityobj.value;
    var conv = '';
    var diff = '０'.charCodeAt(0) - '0'.charCodeAt(0);
    var ch;
    for (i = 0; i < quantity.length; i++) {
        ch = quantity.charAt(i);
        if ('０' <= ch && ch <= '９') {
            conv += String.fromCharCode(ch.charCodeAt(0) - diff);
        } else {
            conv += ch;
        }
    }
    quantity = conv.replace('/[^0-9]/', '');
    if (isNaN(quantity = parseInt(quantity))) {
        quantity = 0;
    }
    quantity = Math.max(min, quantity);
    quantity = Math.min(max, quantity);
    quantityobj.value = quantity;
    if (isNaN(price = parseInt(price)) || quantity < 1) {
        totalobj.value = '※自動計算';
    } else {
        totalobj.value = quantity * price;
    }
}