When value change in first textbox and press tab next text box focus not working

hi,

i m using below code for tab key press then focus on next textbox its working for tab but when i changed value in first text box then  press tab then next text box value focus not selected if how can i show selected value in second textbox if value show

update panel also use all textboxes inside update panel

var lastFocusedControlId = "";

function focusHandler(e) {
document.activeElement = e.originalTarget;
}

function appInit() {
if (typeof (window.addEventListener) !== "undefined") {
window.addEventListener("focus", focusHandler, true);
}
Sys.WebForms.PageRequestManager.getInstance().add_pageLoading(pageLoadingHandler);
Sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(pageLoadedHandler);
}

function pageLoadingHandler(sender, args) {
lastFocusedControlId = typeof (document.activeElement) === "undefined"
? "" : document.activeElement.id;
}

function focusControl(targetControl) {
if (Sys.Browser.agent === Sys.Browser.InternetExplorer) {
var focusTarget = targetControl;
if (focusTarget && (typeof (focusTarget.contentEditable) !== "undefined")) {
oldContentEditableSetting = focusTarget.contentEditable;
focusTarget.contentEditable = false;
}
else {
focusTarget = null;
}
targetControl.focus();
if (focusTarget) {
focusTarget.contentEditable = oldContentEditableSetting;
}
}
else {
targetControl.focus();
}
}

function pageLoadedHandler(sender, args) {
if (typeof (lastFocusedControlId) !== "undefined" && lastFocusedControlId != "") {
var newFocused = $get(lastFocusedControlId);
if (newFocused) {
focusControl(newFocused);
}
}
}

Sys.Application.add_init(appInit);

thanks in advance