function changeSum(num)
{
	if (num==0) num = selected;
	selected = num;
    obj = document.getElementById('sum');
	try{
		if (num >= condition)
		{
			document.getElementById('promotion').disabled = false;
		}
		else
		{
			document.getElementById('promotion').disabled = true;
			document.getElementById('promotion').checked = false;
		}
		if (document.getElementById('promotion').checked)
		{
			promo = promotion_price + " " + currencyText + " + ";
			promo_price = promotion_price;
		}
		else
		{
			promo = '';
			promo_price = 0;
		}
	}
	catch(e)
	{
		promo = '';
		promo_price = 0;
	}
    switch (num) {
        case 1:
            obj.value = " " + price_1 + " " + currencyText + " + " + promo + shippingCost + " " + currencyText + " = " + (shippingCost + price_1 + promo_price) + " " + currencyText;
            document.getElementById('numItems_1').checked = true;
            break;
        case 2:
            obj.value = " " + price_2 + " " + currencyText + " + " + promo + shippingCost + " " + currencyText + " = " + (shippingCost + price_2 + promo_price) + " " + currencyText;
            document.getElementById('numItems_2').checked = true;
            break;
        case 3:
            obj.value = " " + price_3 + " " + currencyText + " + " + promo + shippingCost + " " + currencyText + " = " + (shippingCost + price_3 + promo_price) + " " + currencyText;
            document.getElementById('numItems_3').checked = true;
            break;
        case 4:
            obj.value = " " + price_4 + " " + currencyText + " + " + promo + shippingCost + " " + currencyText + " = " + (shippingCost + price_4 + promo_price) + " " + currencyText;
            document.getElementById('numItems_4').checked = true;
            break;
        case 6:
            obj.value = " " + price_6 + " " + currencyText + " + " + promo + shippingCost + " " + currencyText + " = " + (shippingCost + price_6 + promo_price) + " " + currencyText;
            document.getElementById('numItems_6').checked = true;
            break;
    }
}