I worked it out
For anyone else who might want to modify this functionality what I did was create a template override for the module then in the detault.php file search for
<a href="<?php echo $item->link;?>" <?php echo ArticlesSliderHelper::parseTarget($options->item_link_target);?>>
<?php $img = ArticlesSliderHelper::getAImage($item, $params);
echo ArticlesSliderHelper::imageTag($img);?>
</a>
and change to:
<a href="<?php $urls = json_decode($item->urls);
echo $urls->urla;?>"
<?php echo ArticlesSliderHelper::parseTarget($options->item_link_target);?>>
<?php $img = ArticlesSliderHelper::getAImage($item, $params);
echo ArticlesSliderHelper::imageTag($img);?>
</a>
I hope this helps someone else