function recalc(){
    $("[id^=total_item]").calc(    // the equation to use for the calculation
    "qty * price",    // define the variables used in the equation, these can be a jQuery object
    {
        qty: $("input[name^=qty_item_]"),
            if ($("[id^=price_item_]").length > 0) {
         price: $("[id^=price_item_]")
            }
    },    // define the formatting callback, the results of the calculation are passed to this function
    function(s){
      // return the number as a dollar amount
      return "$" + s.toFixed(2);
    },
        // define the finish callback, this runs after the calculation has been complete
    function($this){
      // sum the total of the $("[id^=total_item]") selector
      var sum = $this.sum();

      $("#grandTotal").text(        // round the results to 2 digits
      "$" + sum.toFixed(2));
    });
    }