Hiding the "Next" Button AS3

Question

Hi Apologies if this has been discussed before.
I have a small microsite built using Flash 4. It contains 5 'pages' assigned to individual keyframes, each keyframe separated by 5 frames (F5s). Each Keyframe is labelled 'page1' through to 'page5'. I have a navigation bar for the entire site which includes NEXT and PREVIOUS buttons. When the user reaches the LAST PAGE/KEYFRAME I do not want the NEXT BUTTON to show. I suspect it is something simple like nextbutton.visible = true - but I've spent a day trying to work out how to do this but without success.
I am using AS3 and the existing coding is shown below. Any help much much appreciated.
Thanks George
nextbutton.addEventListener(MouseEvent.CLICK, nextPage);
previousbutton.addEventListener(MouseEvent.CLICK, prevPage);
function nextPage(event:MouseEvent):void {
    var thisLabel:String = MovieClip(root).currentLabel;
    var thisLabelNum:String = thisLabel.replace("page", "");
    var curNumber:Number = Number(thisLabelNum);
    if (curNumber < 5) {
        var nextNum:Number = curNumber + 1;
        MovieClip(root).gotoAndStop("page" + nextNum);
function prevPage(event:MouseEvent):void {
    var thisLabel:String = MovieClip(root).currentLabel;
    var thisLabelNum:String = thisLabel.replace("page", "");
    var curNumber:Number = Number(thisLabelNum);
    var prevNum:Number = curNumber - 1;
    MovieClip(root).gotoAndStop("page" + prevNum);

Answer 1

Hi Ned
I re-read your suggestion AFTER I had posted my reply and I'm delighted to say it now works.
Unfortunately, I have another related problem that you may be able to help with.
On the Home Page (i.e. KEYFRAME 1) there are a series of button links that take me to the other keyframe/pages. I also need the NEXT BUTTON icon to hide when that keyframe is accessed from KEYFRAME 1 - here is the code:
stop();
leftbutton1.addEventListener(MouseEvent.MOUSE_DOWN, leftbutton1pressed);
function leftbutton1pressed(event:MouseEvent){
    gotoAndStop("page2");
leftbutton2.addEventListener(MouseEvent.MOUSE_DOWN, leftbutton2pressed);
function leftbutton2pressed(event:MouseEvent){
    gotoAndStop("page3");
leftbutton3.addEventListener(MouseEvent.MOUSE_DOWN, leftbutton3pressed);
function leftbutton3pressed(event:MouseEvent){
    gotoAndStop("page4");
leftbutton4.addEventListener(MouseEvent.MOUSE_DOWN, leftbutton4pressed);
function leftbutton4pressed(event:MouseEvent){
    gotoAndStop("page5");
So if I use the NEXT/PREVIOUS BUTTON from any other page it works perfectly but not if I click the button on KEYFRAME 1. If I add nextbutton.visible = false;  at the end of the above code I get Error 1120: Access of undefined property next button.
Any help gladly recieved.
Thanks
George