Rewriting ../<content> URI and Apache mod_proxy (using mod_proxy and mod_rewrite for static content?)

Question

I'm trying to mask a IIS server running a .net application and make it accessible only through an Apache proxy server. I've added this to my httpd.conf

 ProxyRequests Off

 <Proxy *>
 Order deny,allow
 Allow from all
 </Proxy>

 ProxyPass /mypp http://<my iis host>/My_App_root_uri/
 ProxyPassReverse /myapp http://<my iis host>/My_App_root_uri/

It works, i can access my application using http://myapp/asp/Main.aspx but i'm trying to improve my solution. I would like to make it accessible using just this URI instead "http:///myapp"

Two problems:

1. I don't know how to make Main.aspx the default serving content for/myapp
2. I just cannot chroot http:///My_App_root_uri/asp/ in my proxy directives because /asp/*.aspx file use "../resource_file" for static content. I think i should find a way to rewrite these url, or something, before proxying

tnx in advance for help!