This is from Sony's Tablet S support site, it looks like you can create a 'generic' remote where you can add in your own commands:
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Is there an update to the remote control software that will bring it to a Logitech Harmony type level. Seems a shame to have such a large screen and only be able to control a single device at a time and without macros. Ex. Watch TV button starts TV+Receiver+ Cable box and sets inputs. USER-981683
Newbie
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Hello,
Thank you for your Post.
The Media Remote Application does not support Macros, However here is an alternate solution that may work for you.

Press Apps in the upper right Corner
Select “Remote Control”
Press the “Register Device” Plus Circle
Choose “Learn from a remote control”
Press Next
In the Drop down Category choose “other” at the bottom of the list
Press Next
Press the Right Arrow at the top of the Remote template and you will see a blank remote.

From this blank remote you can create a “Multi-Remote Command Console” and use all your separate remotes to teach the key commands for functionality to this new Hybrid Remote.