Again Style Endnote 20 "empty field" handling

My style needs the “series title” and “series volume” field in brackets. As long both fields are filled, everthing works fine, but in some entries the series number is empty. I managed similar issues by using the “Link adjacent text”, but this time I am completely without the right idea to fix the issue. If the series Volume field is empty, the bracket and the dot are missing. Any help?

Author.| Year.| Title.| (Series Title|°Series Volume).|°Place Published: Publisher.

I haven’t tested the below as I am on holiday without my endnote computer!

but I think something like the below should work. it might need some further tweaking.

Author|.°Year|.°Title|.°(|Series Title|°Series Volume|).|°Place Published:|°Publisher|.