Using a function to set x position

programming flash
1

I’ve declared a global variable called [COLOR=DarkRed]thumbSpace[/COLOR].
I have an [COLOR=DarkRed]xmlLoaded[/COLOR] function that loads in thumbnails from an xml file using a loop.
I have an event listener call the [COLOR=DarkRed]thumbLoaded[/COLOR] function when the thumbnail is done loading.

The [COLOR=DarkRed]thumbLoaded[/COLOR] function returns the width of each thumbnail.

function thumbLoaded(event:Event):Number {
    return event.target.width;
}

Inside of the [COLOR=DarkRed]xmlLoaded[/COLOR] function I have the following lines of code:

thumbSpace += thumbLoaded();

I keep getting the "error message 1136: Incorrect number of arguments. Expected 1."�

What am I doing wrong?? I’m trying to use the [COLOR=DarkRed]thumbLoaded[/COLOR] function to set the X position of my thumbnails.