Apache reverse proxy

Dear ALL

I am a newbie at Reverse Proxy and my web servers are Windows Based (IIS in particular). I will be using mod-security with Apache in Reverse-proxy Mode. Now I have a particular requirement with respect to apache working in reverse-proxy mode

In my netwrok there are different internal web servers hosting different web applications eg
i have three webserver(IIS) and they have different web applications serverd

let say the websites are :http://internal1.example.com hosted on internal1 machine
http://internal2.example.com hosted on internal2 machine and http://internal3.example.com hosted on internal3 machine

so my query is that my reverse proxy should work in such a way that any external request from Internet World
a)for internal1.example.com should map to internal1.example.com and
b)internal2.example.com should map to internal2.example.com and
c) internal3.example.com should point to internal3 .example.com

so in all there are three web servers hosting 3 web websites. so my questions is what will be the reverse proxying configuration and architecture for this scenario ?


thanks
Jaspreet