You can pass a single parameter to a macro by enclosing the value of the parameter in parentheses; for examples, see the predefined macros for RTF output listed in Table 37-2. DITA2Go evaluates the parameter as an expression, and the result of the expression is captured in predefined macro variable $$_macroparam. You can reference $$_macroparam in the same macro, and if you need to keep it around, assign its value to another macro variable.
For example, suppose you have a pair of before-and-after macros that surround the body of content intended to be rendered as a note:
[NoteBefore] <p class="notehead"><$$_macroparam></p> <p class="notebody">
You could change the heading to reflect the severity level of the note by invoking the macro like this:
<$NoteBefore("Warning")>
<$NoteBefore("Note")>