AS+XML: variable is "300" but early after "NaN"

programming flash
1

inside the processXML-function the trace(my_thumb_distance) shows the right content: 300. outside the function it traces “NaN”.

why is the variable my_thumb_distance outside the function “not a number” anymore?

thank you for your help!
any ideas to fix it?

var columns:Number;
var my_x:Number;
var my_y:Number;
var my_thumb_width:Number;
var my_thumb_height:Number;
var my_thumb_distance:Number;
var my_images:XMLList;
var my_total:Number;

var myXMLLoader:URLLoader = new URLLoader();
myXMLLoader.load(new URLRequest("content.xml"));
myXMLLoader.addEventListener(Event.COMPLETE, processXML);

function processXML(e:Event):void {
    
    var myXML:XML = new XML(e.target.data);

    columns = myXML.@COLUMNS;
    my_x = myXML.@XPOSITION;
    my_y = myXML.@YPOSITION;
    my_thumb_width = myXML.@WIDTH;
    my_thumb_height = myXML.@HEIGHT;
    my_thumb_distance = myXML.@DISTANCE;
    my_images = myXML.IMAGE;
    my_total = my_images.length();[COLOR=Red]

[/COLOR]    [COLOR=Red]trace(my_thumb_distance);[/COLOR]

    myXMLLoader.removeEventListener(Event.COMPLETE, processXML);
    myXMLLoader = null;
}

[COLOR=Red]trace(my_thumb_distance);[/COLOR]