Thread: Externally included file and project level #define?

Don't know exactly which forum to post this in... anways below is my problem:

1) I have a project. (obviously)
2) In this project I have a "Resource.h" that has a series of #defines
3) I include a header & cpp from a completely different directory and in these files they need to know about some of the #define(s) in the project's "Resource.h".

Problem is when I try and compile/build the sucker it complains about "error C2065: 'IDD_CONTROL': undeclared identifier (for the externally included header & cpp). I know there is a way to get this to work without having to include the "Resource.h" as I've seen a project do it, but even staring at it for 30 minutes comparing settings I can't figure out what they are doing that I'm not.

Specifically including in the external header:

#include "..\project folder\project\Resource.h" <-- this works, but this external header & cpp are shared among multiple projects so I don't want to do that.

Any ideas? I'm using Visual Studio's IDE.