Question:

Is it possible to pass the inverse apostrophe Alt 96 as a macro argument?

  Macro calc
  Set var1 = var2 * var3 %1 times var4

Where I intended %1 to a `, which would have effectively blanked out the
second multiplication.

Answer
    
2. The inverse apostrophe is always interpreted as a comment, so it never
survives beyond the line in which it appears.  You could accomplish the same
thing as follows:
    
    
  macro calc
  set var1 = {var2} times {var3}
  if "%1"="" then set var1 = {var1} times {var4}
  /
    
Then pass any character (except the inverse apostrophe) to avoid the last
multiplication.