How to proxy/rewrite URL for preview pages

[JosepC]

Hello:
I've installed SiteBuilder on a Lan host not visible from internet.
I've configured Apache with Proxy + ReverseProxy entries in order to redirect the public Internet URL to the private one.
Ej: http://builder.mypublicdomain.com <==> http://sitebuilder.host.internaldomain.int
.
All works fine except for preview.
When user whats to preview the site, a popup window is open, and the URL sow is the internal one: http://sitebuilder.host.internaldomain.int/xxx
.
Any one can help me on thys issue?
Thanks