View Webserver Form Internal and Extenal

[just4net]

Hi
I use centos 5.8 + kloxo for my webserver and publish site in the internet , every thing is fine when people see my website from internet.
But problem is :
In my office and lan network [ip range : 192.168.170.0-254] when we are want see website go from internet and show website (In dns manager I set WAN ip address)
If I set Lan IP address in dns , nobody can see website from internet .

My Lan network is windows base with active directory and centos server is Separate pc with DSL line

How can I set wen user in my office want see website open it from local network and outside of my office see website with my WAN IP address