Need a selection in query_posts

Hello,

I’m trying to change the index.php of my theme to something like this:

If exists more than 1 post from the same day (the last day which has a post)

show them all(!) in regular view

else

show last post in single view

The 2nd part I already have and it works:

<?php if (is_home()) {query_posts('showposts=1&cat=-1');} ?>
<?php $wp_query->is_single = true; ?>

Additional I have excluded 1 category.

Background is that I want to show basically only the last post on the index.php. But if I post more than 1 time a day, my first post of the same day would be already “hidden” and not actually allthough it is actually.

Therefore I need that special loop.
Does anyone have an idea for the 1st part? My PHP-understanding isn’t really big.

Thanks to you.
Ric