Drop-down archive menu category specific?

Hi,

I am trying to create a drop down menu of post archives by month. I have used the following code to achieve this…

<select name="archive-dropdown" onchange="document.location.href=this.options[this.selectedIndex].value;">
  <option value=""><?php echo esc_attr( __( 'Select Month' ) ); ?></option>
  <?php wp_get_archives( 'type=monthly&format=option&show_post_count=1' ); ?>
</select>

This works but does anyone know how to make it category specific?

Thanks.