title: switch wordpress theme base on URL
body: <p>I have a wordpress website that host several themes inside it. 
  Now I want to switch the themes for visitor base on the URL that they enter.
  for example : </p>
  
  <p>my WP website is at <a href="http://www.myblog.com/wp/" rel="nofollow">http://www.myblog.com/wp/</a> </p>
  
  <p>but if user enter : </p>
  
  <p><a href="http://www.myblog.com/wp?theme=twentyten" rel="nofollow">http://www.myblog.com/wp?theme=twentyten</a> -> using twentyten theme</p>
  
  <p>and if user enter : </p>
  
  <p><a href="http://www.myblog.com/wp?theme=mycustomtheme" rel="nofollow">http://www.myblog.com/wp?theme=mycustomtheme</a> ->using mycustometheme </p>
  
  <p>then
  is there any plugins available out there? I've been searching for days but no one seam to work for me.</p>
  
  <p>Any suggestion is very appreciated! </p>
  
  <p>Thanks </p>