plugin rpm macro

I looked at the preupgrade plugin 'whiteout'.  And in the code I see 
where it gens a macro '_dependency_whiteout' and then appends a list of 
'package>requires' strings to it.  My question is, for testing, can I 
put this macro into /etc/rpm/macros and then will yum/rpm use it?  I 
tried one test already but it didn't seem to work.  But maybe I didn't 
name the package correctly.

Regards,
Gerry