// Generic function
function obtainElement(eid){

    if (document.all) { //IS IE 4 or 5 (or 6 beta)
        var element = eval( "document.all." + eid);
    }
    if (document.layers) { //IS NETSCAPE 4 or below
        var element = document.layers[eid];
    }
    if (document.getElementById &&!document.all) {
        var element = document.getElementById(eid);
    }
    return element;
}


// Increase quantity
function addBy(element){
	var el = obtainElement(element);
	var qt = parseFloat(el.value);
	qt += 1;
	el.value = qt;
	checkTotal();
}

// Decrease quantity
function reduceBy(element){
	var el = obtainElement(element);
	var qt = parseFloat(el.value);
	qt -= 1;
	if (qt < 0)
		qt = 0;
	el.value = qt;
	checkTotal();

}

//Check quantity and update total
function checkTotal(){
	var total = 0;
	var fnum = 1; 
	for (fnum=1;fnum<=10;fnum++)
	{
		var it = "item"+fnum;
		var pc = "price"+fnum;
		try{
		   quantity = obtainElement(it).value;
		   price    = obtainElement(pc).value;
		total += parseFloat(quantity) * parseFloat(price);
		   }
		catch(err){}
	}
	var tot = obtainElement("sum");
	tot.value=total;
}