shortcode executed before content

Hi.

I have this in my functions.php:

add_shortcode('ataglance', 'ataglance_function');
function ataglance_function() {
?>
<table>
<!-- // generate table from xml file -->
</table>
<?php
}

And this in my page:

test copy
[ataglance]

However, the page output (from the_content) is

<table>...</table>
test copy

How can I make sure the code is executed in order?

Thanks