I think you want an event handler for the input elements. Maybe
something like this? Instead of finding the column in the row above, I
just looked for the Nth price in the row above. That turned out to be
the most complicated part. The DOM defines a .rowIndex property for TR
elements but there is no .colIndex property for TD elements.
$(document).ready(function() {
$("input").bind("keyup focus", function(){
var $inp= $(this);
var pos = $inp.parent("tr").children().index($inp.parent("td"));
$inp.next("span").text( // span following input
(+$inp.val() || 0) * // value of input times price in row
above
$inp.parent("tr").prev().find(".price").eq(pos).text()
);
}).trigger("keyup");
});
I probably left a mistake or two in there...
