dynamic_sidebar not returning/echoing/printing HTML, need help…

Can anyone explain why these code snippets wouldn’t echo/print/return this function with the li tags? In fact, nothing I try to execute (except for the function) prints out!

if ( !dynamic_sidebar( 'right_column_on_two_column_layout' ) ) {
	return "<li>" . dynamic_sidebar( 'right_column_on_two_column_layout' ) . "</li>";
}

if ( !dynamic_sidebar( 'right_column_on_two_column_layout' ) ) {
	echo "<li>" . dynamic_sidebar( 'right_column_on_two_column_layout' ) . "</li>";
}

if ( !dynamic_sidebar( 'right_column_on_two_column_layout' ) ) {
	echo "<li>";
	dynamic_sidebar( 'right_column_on_two_column_layout' );
	echo "</li>";
}