Organizing Widgets

I am in the process of creating a template that I can use on the fly for building sites for clients. I plan on having several, dynamically styled, widget areas (sidebars). On the top and bottom. I am allowing up to 4 widgets to be displayed in a row (side-by-side). When there are more than 4 widgets in a widget area it will create a new row.

I have created the following function to assign class names to the elements containing the widgets based on how many appear in each row. I can now use CSS to control the size of the widgets in each row to fill the width of the content element.

/* Creates rows of widgets and adds a class name based on the number in each row */
function dicey_add_widget_classes() {

	global $wp_registered_widgets;

    $sidebars = wp_get_sidebars_widgets();
	$row_max = 4;

    /* Loop through the widgets in each sidebar */
    foreach($sidebars as $sidebar=>$widgets) {

        $widget_count = count($widgets);
		$widgets_by_row = array();

		/* If the sidebar has at least one widget organize them into an array by rows */
		if($widget_count > 0) {
			foreach($widgets as $index=>$widget) {
				$row = floor($index/$row_max);
				$widgets_by_row[$row][$index] = $widget;
			}
		}

		/* If there is at least one row: */
		/* Loop through the previously created rows and their respctive widgets, adding the proper class name */
		if(!empty($widgets_by_row)) {
			foreach($widgets_by_row as $row=>$widgets) {
				foreach($widgets as $widget) {
					$span = count($widgets)%$row_max;
					if(count($widgets) == $row_max) {
						$wp_registered_widgets[$widget]['classname'] = 'widget span-' . $row_max;
					}
					else {
						$wp_registered_widgets[$widget]['classname'] = 'widget span-' . $span;
					}
				}
			}
		}
    }
}

What I would like to achieve next is this: I would like the ability to dynamically create an element that acts as a row container. Let’s say for example I have 6 widgets in the “Top” widget area. The output would appear like so:

<div class="row1_container">
     <div id="widget1" class="widget span-4">
    	<!--Content-->
    </div>
     <div id="widget2" class="widget span-4">
    	<!--Content-->
    </div>
     <div id="widget3" class="widget span-4">
    	<!--Content-->
    </div>
     <div id="widget4" class="widget span-4">
    	<!--Content-->
    </div>
</div>
<div class="row2_container">
     <div id="widget5" class="widget span-2">
    	<!--Content-->
    </div>
     <div id="widget6" class="widget span-2">
    	<!--Content-->
    </div>
</div>

Basically, I would like to be able to access the ‘before_widget’ attribute when the first element in a new row is reached and the ‘after_widget’ attribute when the last element in a row is reached. I have no problem determining the widget location within a row, just need to know how to modify the ‘before_widget’ and ‘after_widget’ attributes.

I have exhausted my Googling abilities in this matter. Thanks for your help!