How to Slipstream a Service Pack and a CU together

I am currently running SQL 2008 R2 SP1 CU 6.  I would like to upgrade if you will to SP2 and CU5 at the same time.  Is there a way to create a single install of SP2 and CU5 so that I only have to run the install one time and get both SP2 and CU5 installed?

I know how to slipstream the RTM media, SP2, and CU5 together to create media that I use to do a clean install.  That is not what I want to do here.  Since SQL is already installed I want to apply SP2 and CU5 at the same time without having to run two setups.

Thanks

Michael