First widget with unique div style

Is it possible to add something like ‘before_first_widget’ with functions.php?
I need to give the first widget of each page a different style to the second. I’ve spent days on this with no joy!

This is my current code. I can add a ‘1’ to my div but this is global and it’s only needed on the second div. Help please!!

<?php
for($i =0; $i <2; $i++)
if ( function_exists(‘register_sidebar’) )
register_sidebar(array(
‘name’ => ‘Sidebar’,
‘before_widget’ => ‘<div id=”box’.++$i.’“>’,
‘after_widget’ => ‘</div>’,
‘before_title’ => ‘<h2>’,
‘after_title’ => ‘</h2>’,
));