I'm trying to create a set of rpm files to install the requirements
for a program. I found a great utility named cpanspec that will
create a spec file for perl modules and have started building rpm
files.

I was able to create an rpm file for Business::CreditCard as a
regular user. Now I'm trying to build another module that
requires B::CC, and rpmbuild -ba fails saying that I am missing
B::CC. I don't want to install it just to create another rpm
file. Is there a way to make rpmbuild "think" that B::CC is
installed in the build environment without installing it on
the system?

Since a .spec file takes shell commands you could export PERL5LIB=/some/dir inside of it which, if you run it from the CLI and check with 'perl -V', should show the path added to @INC?