Styling children of pages

I would like to edit the list image for subpages but don’t know how! I’m using <?php wp_list_pages(‘exclude=485,519&sort_order=ASC&sort_column=post_name&date_format=(y.m.d)&show_date=modified&title_li=’); ?>
and it’s generating:

< ul >
< li class=”page_item” >< a href=”http://www.link.here&#8221; >Link< /a >< /li >
< ul >
< li class=”page_item” >< a href=”http://www.link.here&#8221; title=”subpage” > Sub page < /a > (06.01.24) < /li >
< /ul >
< /ul >

Where could I add a class to the
< ul > tag within the first
< ul > tag?

Hope you understand what i’m after (english isn’t my first language)