Redirect to a internal server & port

Hi people! 

I'm setting up a server that the application needs a redirect to a specific location (because the page isnt in the same host as the IIS, its in another host in my internal lan and running in an specific port). 

Here its the example:

The request on the internet comes from: 

http://www.myserver.com/NEWAPPLICATION/  

and i need that IIS do a internal handling operation with this page (and whatever sub-internal directories have) like this (this will be the internal request:)

http://10.1.1.99:1111/

And whats the problem? That when i do this, the external client (that obviusly dont have access to my internal lan), cant connect to it, because the HTTP Redirection in IIS its explicit

I need that instead of showing the internal IP:port, the IIS go and handle the operation like itself and shows it in the common 80 port that i have public, and also, all the relative sub-sites, go to the same place.

Like if a user types:

http://www.myserver.com/NEWAPPLICATION/subdirectory/index.html

Internally the iis handle this and do a internal request to this another internal server (that obviusly has local connection, no firewalls between this IIS and "newapplication" server

http://10.1.1.99:1111/subdirectory/index.html

This its that all /NEWAPPLICATION/ requests always go to this http://10.1.1.99:1111/  server.

I really think that its so easy to do, but really, after some hours searching, i dont have a good answer to this, because all that i see about redirects, shows external adresses, and no internal redirects.

I'm working with Windows Server 2008 R2, IIS7 and i have the Redirect HTTP IIS feature installed.

Thank you very much for your help!