Hi Susan,
Your definition of opening and closing parentheses is opposite mine.
For me, the opening one would be: "(" and closing: ")"
If you are doing this as you type, do you really need a macro?
Type your parentheses, and select the text.
Apply your style. You can do that with a keyboard shortcut attached to the style.
Assigning Keyboard Shortcuts in Microsoft Word 2007-2021 (365)
If you need a macro, do you want the style applied to the parentheses as well as the text?