Hi,
use this script by using JQuery
function calculateGrandTotal() {
var Amount = 0;
$("#ctl00_MainContent_grid input[name*='txtAmount']").each(function (index) {
if ($.trim($(this).val()) != "")
if (!isNaN($(this).val()))
Amount = Amount + parseFloat($(this).val());
});
$("#ctl00_MainContent_grid span[id*='lblDisplay']").text(Amount);
}
now call this function on javascript by using javascript event onkeyup='calculateGrandTotal();'