How add custom filter to admin custom post type pagination?

I have select filter in custom post type write panel.
Post filtered by custom field edate_m:

add_filter( 'parse_query', 'sort_calendar_by_date' );
function sort_calendar_by_date($query) {
    global $pagenow;

if(is_admin() && $pagenow=='edit.php' && isset($_GET['post_type']) && isset($_GET['post_type'])=='calendar' && $_GET['sortby_d'] =='0' && $_GET['sortby_m'] !='0'){
	        $query->query_vars['meta_key'] = 'edate_m';
		$query->query_vars['meta_value'] = $_GET['sortby_m'];
	}
}

All working perfect. But if I pressing to page 2, filter are resseting and variable &sortby_m=1 in address line in dissapearing.

How I can implement custom fields filter variable to pagination? Thank you!