A shortcode slider with Flexslider

Hello!

I try to make a shotcode slider with flexslider using this tutorial:

So i want to modify the post query to implement a category option in my shortcode.

Someone can help me please?

I try that:

function e_insert_slider($atts, $content=null){

$slider= e_get_slider();

$categoryname = $content;

return $slider;

}

add_shortcode('e_slider', 'e_insert_slider');
function e_get_slider(){

	$slider= '<div class="flexslider">
	  <ul class="slides">';

	// assign the variable as current category

// run the query
query_posts("&categoryname=".$categoryname);

	if (have_posts()) : while (have_posts()) : the_post();
		$img= get_the_post_thumbnail( $post->ID, 'large' );

		$slider.='<li>'.$img.'</li>';

	endwhile; endif; wp_reset_query();

	$slider.= '</ul>
	</div></br>';

	return $slider;
}

/**add template tag- for use in themes**/

function e_slider(){

	print e_get_slider();
}