[O] macro replacement in code block?

[David Rogoff]

Hi.

Trying to set up a large orgmode file with source code for several files that 
is extracted using tangle and also exported to HTML for documentation (source 
is verilog-mode).  It works but I’m trying to clean it up by using orgmode 
macros.  However, it seems like these are not replaced when inside code blocks. 
 I found a couple of references to this by searching Google but they were very 
terse and also referenced from orgmode function that doesn’t exist.  Can anyone 
point me to some documentation or example?

Thanks,

 David 

using gnu emacs 25.2 Linux / orgmode 9.1.2