return false must be hit after calling certain command

Hi Experts, I need to make the "return false", work after calling "document.getElementById("imageid").src="E:\Products\"+picNumber + ".jpg";" As the code below the "return false" will no longer work. Is there any alternatives to keep this thing work?  


<script>
   $(function()
   {
     $('#myTable button.Showbutton').click(function() {
       picNumber = ($(this).closest('tr').find('td:eq(4)').html());
       document.getElementById("imageid").src="E:\Products\"+picNumber + ".jpg";
       return false;
     });
   });
</script>

               <div id="Subnav4">
                  <div>  
                     <img src="" id="imageid" alt="x-men" style="width:250px; height:250px;">
                  </div>
               </div>