Horizontal Scrollbar with Dynamic Width

I need to find a way how to make the horizontal scrollbar appear without hardcoding the width.

HTML

<script src="http://jscrollpane.kelvinluck.com/script/jquery.jscrollpane.min.js"></script>
<link rel="stylesheet" href="http://jscrollpane.kelvinluck.com/style/jquery.jscrollpane.css">
<div class="internalTabs recentlyViewedReports">
  <span class="internalTab active">Carousel</span>
</div>
<div class="internalTabsContent scrollerContent recentlyViewedReports">
  <div class="internalTabContent active">
    <div class="scroll-pane">
      <div class="scrollInner">

        <div class="scrollableItem">
          <a href="#">

						<span class="title">##Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
        <div class="scrollableItem">
          <a href="#">

						<span class="title">Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
        <div class="scrollableItem">
          <a href="#">

						<span class="title">Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
        <div class="scrollableItem">
          <a href="#">

						<span class="title">Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
        <div class="scrollableItem">
          <a href="#">

						<span class="title">Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
        <div class="scrollableItem">
          <a href="#">

						<span class="title">**Scroll pane item</span>
						<span class="content">Dec. 11, 2013  |  12:34PM</span>
					</a>
        </div>
      </div>
    </div>
  </div>
</div>

CSS

/* Internal Tab Content*/

.internalTabs {
  margin-top: 16px;
  margin-left: 12px;
  display: inline-block;
}

.internalTabs .internalTab {
  background: #e0e0e0;
  padding: 7px 10px 7px 10px;
  display: inline-block;
  color: #763c5e;
  font-weight: bold;
  -webkit-border-radius: 4px;
  -moz-border-radius: 4px;
  border-radius: 4px;
  margin-right: 7px;
  cursor: pointer;
  padding-right: 24px;
  min-width: 142px;
  background: #e0e0e0 url("images/purpleSelectDownArrow.png") 97% center no-repeat;
}

.internalTabs .internalTab.active {
  color: #763c5e;
  -webkit-border-bottom-left-radius: 0;
  -moz-border-radius-bottomleft: 0;
  border-bottom-left-radius: 0;
  -webkit-border-bottom-right-radius: 0;
  -moz-border-radius-bottomright: 0;
  border-bottom-right-radius: 0;
}

.internalTabContent {
  height: 0;
  overflow: hidden;
  border: none;
  background: #ffffff;
  position: relative;
  bottom: 2px;
  -webkit-border-bottom-right-radius: 7px;
  border-bottom-right-radius: 7px;
  -moz-border-radius-bottomright: 7px;
  -webkit-border-bottom-left-radius: 7px;
  border-bottom-left-radius: 7px;
  -moz-border-radius-bottomleft: 7px;
}

.internalTabContent>.threeColumnLayout {
  padding: 13px;
}

.internalTabContent>.fullWidth {
  margin: 13px;
  margin-bottom: 0;
  width: 97.5%;
}

.internalTabContent.active {
  height: auto;
  overflow: visible;
  border: 2px solid #e0e0e0;
}

.internalTabContent.active {
  display: block;
}

.internalTabs .internalTab.disabled {
  color: #777777;
  background: none;
}

.internalTabs.savedReportsTabs .internalTab {
  background: #e0e0e0;
  -webkit-border-radius: 4px;
  -moz-border-radius: 4px;
  border-radius: 4px;
  margin-bottom: 24px;
  color: #777777;
}

.internalTabs.savedReportsTabs .internalTab.active {
  color: #763c5e;
}

.internalTabsContent.savedReportsTabs .internalTabContent {
  border: none;
  bottom: auto;
}

.internalTabs.recentlyViewedReports {
  margin-left: 0;
}

.internalTabsContent.recentlyViewedReports...

JavaScript

$(document).ready(function() {
  $('.internalTabs .internalTab').click(function() {
    var clickedTabIndex = $(this).index();
    if ($(this).hasClass('active')) {
      $(this).removeClass('active');
      $(this).parents('.internalTabs').next('.internalTabsContent').children().eq(clickedTabIndex).removeClass('active');
    } else {
      $(this).siblings().removeClass('active');
      $(this).parents('.internalTabs').next('.internalTabsContent').children('*').removeClass('active');
      $(this).addClass('active');
      $(this).parents('.internalTabs').next('.internalTabsContent').children().eq(clickedTabIndex).addClass('active');
    }
  });

  // calculate width for each scroll pane
  $('.recentlyViewedReports .scroll-pane').each(function() {
    var scrollableItemCount = $(this).children('.scrollInner').children().size();
    var scrollableItemWidth = 270;
    var scrollInnerWidth = scrollableItemCount * scrollableItemWidth;
    $(this).children('.scrollInner').width(scrollInnerWidth);
  });

  // scroll pane script for modals and recently viewed reports
  $('.scroll-pane').each(function() {
    $(this).
    jScrollPane({
      verticalDragMinHeight: 20,
      verticalDragMaxHeight: 20,
      horizontalDragMinWidth: 20,
      horizontalDragMaxWidth: 20
    });
    var scrollpaneApi = $(this).data('jsp');
    var throttleTimeout;
    $(window).bind('resize',
      function() {
        if (!throttleTimeout) {
          throttleTimeout = setTimeout(function() {
            scrollpaneApi.reinitialise();
            throttleTimeout = null;
          }, 50);
        }
      });
  });

});