adding a single sidebar to use above the two sidebars

sorry, I don’t know.
——-
https://www.dvdshop88.com

it is posible, however it depends on how much editing you would like to do.

for instance, you could copy one of the sidebar php files and rename it to t_sidebar.php, then integrate the call of the top-sidebar in l_sidebar.php, change functions.php to 3 sidebars, and style the t_sidebar in style.css.

t_sidebar.php:

<!-- begin t_sidebar -->

	<div id="t_sidebar">

	<ul class="t_sidebarwidgeted">
	<?php if ( function_exists('dynamic_sidebar') && dynamic_sidebar(3) ) : else : ?>

	<h2>Blogroll</h2> <!-- or anything you like, this will only show if no widget is activated in the top sidebar -->
		<ul>
		<?php get_links(-1, '<li>', '</li>', ' - '); ?>
		</ul>

		<?php endif; ?>
		</ul>

</div>
<!-- end t_sidebar -->

changes to l_sidebar.php:

<!-- begin l_sidebar -->

<?php include(TEMPLATEPATH."/t_sidebar.php");?>

	<div id="l_sidebar">

keep the rest as it is.

changed functions.php:

<?php
if ( function_exists('register_sidebars') )
    register_sidebars(3);
?>

style.css – add new lines formating of t_sidebar:

/************************************************
*	Top Sidebar 					     	    *
************************************************/

#t_sidebar {
	float: left;
	width: 406px;
	margin: 40px 0px 0px 0px;
	padding: 0px 19px 20px 19px;
	border-left: 1px solid #E2DDDE;
	font:11px/18px Verdana, Arial, Helvetica, sans-serif;
	}

#t_sidebar ul {
	list-style: none;
	margin: 0px;
	padding: 0px;
	}

#t_sidebar ul li {
	background: none;
	display: block;
	padding: 4px 0px 4px 0px;
	margin: 0px;
	}

#t_sidebar ul li ul li{
	background:transparent url("images/bullet.gif") 0px 11px no-repeat; /* 0px = horizontal position for left, 6px = vertical position from top */
	padding-left: 10px;
	margin: 0px;
	}

#t_sidebar a:link, #l_sidebar a:visited	{ color:#444; text-decoration:none; outline:none; }
#t_sidebar a:hover, #l_sidebar a:active	{ color:#444; text-decoration:underline; outline:none; }

#t_sidebar p{
	padding: 3px 0px 0px 0px;
	margin: 0px;
	line-height: 20px;
	}

#t_sidebar li {list-style: none; }

might need fine-tuning, not tested, but nothing particularly complicated either ??