How can I prevent the 32bit version of a package from updating the 64bit version

Issue

• We have installed the 64bit version of flash-plugin from the Adobe repository
• Red Hat only supply the 32bit version of flash-plugin, however its version (NEVRA) is slightly greater than the Adobe version
• Performing a yum update causes the Red Hat supplied 32bit version to update the 64bit version, but we want to keep the 64bit version and not have the 32bit version installed

# yum update
Loaded plugins: auto-update-debuginfo, rhnplugin, security
This system is receiving updates from RHN Classic or RHN Satellite.
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package flash-plugin.x86_64 0:11.2.202.341-release will be updated
---> Package flash-plugin.i686 0:11.2.202.341-1.el6 will be an update
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package      Arch   Version                  Repository                   Size
================================================================================
Updating:
 flash-plugin i686   11.2.202.341-1.el6       rhel-x86_64-workstation-supplementary-6
                                                                          5.3 M