[Lucene.Net] separating project file from actual code files

[Prescott Nasser]

This seems like it should be obvious, but I'm trying to create a new 
Contrib.Regex project for the Regex stuff. However, when I do this, VS wants to 
put all the .cs files into the build directory where the project file is. How 
do I tell the project file that the actual files for the project should be 
located in another folder?
 
I've taken a look at some of hte other projects but I can't see where this is 
designated
 
~P