Associative Array - How to?

I’m looking to create an array with at least 3 different elements: description, price and quantity, something like this (but not working yet) -

var itemArray:Array = new Array();
itemArray["artwork"] = {description:undefined, price:0.00, quantity:1};

for (var i:Number = 1; i <= count; i++) {
    itemArray["artwork"]*.description = prod_num;
    itemArray["artwork"]*.price = 0.00;
    itemArray["artwork"]*.quantity = 1;
    trace(itemArray["artwork"]*.description); //All UNDEFINED
    trace(itemArray["artwork"]*.price); //All UNDEFINED

    //itemArray["artwork"].quantity exists but it isn't possible to add a series of elements in this array - Why???