Maybe I'm solving this problem in the wrong place.
I'm creating a WiX ComponentGroup, but I have some fiddly path requirements to deal with here (aforementioned PROGRAMDATA constraint)
The problem this causes me is that I'm missing a directory, but maybe I need to hard-code that missing directory as a <Directory> tag in my installer definition XML, then refer to the <DirectoryRef> tag generated by heat.exe which contains the one-level-down information on the files I want?