I believe that all you need to do is buy a CHEAP "All In One" remote that can be programmed with MACROS
I then think that all you need to do is get the HARMONY remote to "learn" this macro from the other remote and away you go - the macro will then be programmed to this button! :-D
This does of course give the added expense of buying an additional remote - but I know that most of us would happily do this as adding MACRO features to the HARMONY range would give the ULTIMATE, reasonably proced remote (perhaps a reason they have been holding back on this addition ??)
I must say that I have not tried this myself yet so I can't say 100% that it works but I do recall reading it somewhere and I intend to do it myself when I get my new set-up sorted out
I really do not see why they do not give the option to programme MACROS??