I've tested using the following syntax, and it does run my code just find
Application.Run "MyReallyLongComplicatedFileName.xla!TestMacro "

However, I want to make my code more flexible, and instead of hardcoding the
filename throughout my code every place I need to run some code from that
XLA, I tried setting it up as an indirect reference, e.g.,
Dim Codefile as AddIn
set CodeFile = "MyReallyLongComplicatedFileName.xla"

then in various parts of my code, call the macros using something more like:
Application.Run CodeFile!TestMacro or
Application.Run CodeFile & "!TestMacro"

but so far, I haven't figured out the syntax to make this type of indirect
code reference work.

Can anyone give me a hint?
Thanks!
Keith