add_action (‘get_sidebar’, ‘myfunction’) not working

Hey there,
I’ve written a plugin that starts with:
add_action('get_sidebar', 'myfunction');
and it doesn’t work unless I change it to:
add_action('get_footer', 'myfunction');

even though the template code is:
<?php get_sidebar(); ?>
<?php get_footer(); ?>

In fact, I can get the plugin to display for just about any other action (or even add_filter) with the exception of “get_sidebar”.

Pity, because that’s EXACTLY where I need it.

Any ideas will make me happy like chocolate cake.

Cheers!