Were you to be able to install software on your local server this wouldn't be too hard. Some combination of Perl / TT / latexmk along with a LaTeX system (e.g. TeXLive or MiKTeX).
I don't know about latexlab mentioned above. The closest thing I know of is http://www.tlhiv.org/ltxpreview/ , which perhaps you could wrap to do what you need (or even write a howto for your users).
