Is there a way to set the RPM file name in the spec file?

[t l roden siep shell com]

Dear RPM List,

In our macros file we have the _rpmfilename macro defined as:

%_rpmfilename       
%%{OS}/%%{NAME}-%%{VERSION}-%%{RELEASE}.%%{OS}.%%{ARCH}.rpm

Is there a way to override this (and other macro) values within the 
spec file definition?

Sincerely,
Tim Roden