Footnote variation required

In the style required by our school students are expected to alternate between two types of footnote, one that uses parenthesis and the other that uses parenthesis plus brackets, as in the following example.

Martin Noth, Numbers. A Commentary (Old Testament Library; trans. James D. Martin; Philadelphia: ‎Westminster John Knox, 1968), 1, 4.

(Martin Noth, Numbers. A Commentary [Old Testament Library; trans. James D. Martin; Philadelphia: Westminster John Knox, 1968], 1, 4) ‎
How is it possible to make Biblioscape alternate between the two formats? It looks like the feature "new-sub style" could work for this, but I don't know since I've never used it. Thanks!

The "New sub-style" just

The "New sub-style" just create a new reference type specific sub-style based on the currently selected one. So you can format references differently based on reference type. I don't understand why you have to alternate between two types of footnote. Is it for the same reference type? 

I have to alternate to

I have to alternate to brackets when I comment and argue around footnote references. This is my advisor's preference. When I don't comment around footnotes, brackets are not used, only parenthesis. I guess that when we comment and elaborate on footnotes the teacher wants to have reference punctuation separated from my footnote text.

I cannot think of a way to

I cannot think of a way to do this automatically.