Hi,
My problem:

I have installed XOOPS on my localhost pc, and in the mainfile it sais:

// XOOPS Virtual Path (URL)
// Virtual path to your main XOOPS directory WITHOUT trailing slash
define('XOOPS_URL', 'http://192.100.110.2/xoops');

But my problem is that people from outside can't reach the side, when I change the IP into my outside Ip it works but then I cant by myself reach the side.
Is there an option to ad 2 IP ranges in the mainfile???

(sorry foor my poor english)

You need to use DNS. Set the URL to something that resolves properly for outside users i.e.http://yoursite.net/xoops . Then for the inside you either need to have that same name resolve to the correct internal IP or make an entry in your "hosts" file:
192.100.110.2 yoursite.net

If you are using a dynamic IP for your internet then get a dynamic DNS service like dyndns.org and use a client that will keep it updated.