xcode 3.1 and openmp

Ok, I'm probably missing something very simple here, but in trying to compile code that uses openmp in xcode, I have selected my compiler as gcc 4.2, and checked the 'Enable OpenMP Support' check box in the build settings, but when I try to build, I get the error, "omp.h: No such file or directory". This is weird because it compiles just fine from the command line (using either gcc44 or nvcc, with appropriate tags). So is there something simple that I'm missing here? All I'm doing is creating a new c command line utility, and throwing "#include <omp.h>" up at the top of the main.c, and try to compile, and I get the error. Xcode is 3.1.3.

Thanks much,

Paul