Beginner having problem with removechild() function

programming flash
1

I’ve created a function that creates a thumbnail bar

function imageLoaded(evt:Event):void
{
var thumb:MovieClip = new MovieClip();
//trace(thumb.x);
thumb.y=710;
addChild(thumb);
thumb.name = gallery_xml.image[currentImage].big;
trace ("thumb "+thumb.name);
thumb.x=currentImage*thumbSpace;
thumb.addEventListener(MouseEvent.CLICK, updateStage);
thumb.addChild(evt.target.content);
thumbDisplayed = true;
currentImage++;
}

What I want to do is when I navigate away from the page I want to remove the thumbnails from the page:

homeBT.addEventListener(MouseEvent.CLICK, ToHome);
// function used to navigate to home page
function ToHome (event:Event):void
{
if (thumbDisplayed = true)
{
removeChild(thumb);
thumbDisplayed = false;
}
if (imageBigDisplayed = true)
{
removeChild(bigLoader);
imageBigDisplayed = false;
}
}

However every time I try to use removeChild(thumb); it gives me this error:

Scene 1, Layer ‘actions’, Frame 16, Line 81 1120: Access of undefined property thumb.

I know it might be because thumb is inside a function but I haven’t been taught any other way to remove the movieclip.

Any help would be great! :}