vBulletin Lose your place in the unread threads list?

There are times when I click into a forum and the list of unread threads is daunting. As the administrator, I try to, or want my staff to look over each thread. Occasionally the thread has a number of posts I read and by the time I click back to the thread list, I've lost my place. The down arrows are still there and I can't remember the thread title to remember where I am in the list.

I would like to add an additional image, another down arrow, to the mix, that will have the appearance of changing colors when it has been clicked on - like what the multi-quote button does in the message display. I've never designed or developed a hack/plug-in, so I was hoping one of the coders could come up with something. I thought it could be done with a little CSS magic, or maybe it should be JavaScript, but ajax would be my choice, just like the multi-quote routine.

These are the 2 images that will be linked to the first new message in a thread:

Here is the current CSS and code (from SHOWTHREAD template), which uses only the first image:

Code:

.tcat {
   background: #D9F1E9;
   color: #666666;
   font: 14pt tahoma,verdana, arial, helvetica, sans-serif; }
.tcat a:link, .tcat_alink {
   color: #333333;
   text-decoration: none; }
.tcat a:visited, .tcat_avisited {
   color: #333333;
   text-decoration: none; }
.tcat a:hover, .tcat a:active, .tcat_ahover {
   color: #000000;
   text-decoration: underline; }
.smallfont {
   font: 11px verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif; }
.inlineimg {
   vertical-align: middle; }

HTML:

<td class="tcat" width="100%">
   <div class="smallfont">
   <if condition="$show['firstunreadlink']">
      <a href="$firstunread"><img class="inlineimg" src="$stylevar[imgdir_button]/firstnew.gif" alt="$vbphrase[view_first_unread]" border="0" /></a>
      <a href="$firstunread"><strong>$vbphrase[view_first_unread]</strong></a>
   </if>
   &nbsp;
   </div>
</td>

I am not concerned about whether the image changes when hovered, only when clicked. Can you help me with the CSS and other code (hopefully ajax)?

Thank you,

Jim
PS: the code I supplied above is not from the default code for vBulletin - I use a custom style. But it's similar.