Child-category in permalink

Hi all,

I’m changing the arrangement of my posts that were in a category (ie. “foo-category/postname”). And now, I want to get some categories as a child categories, so the new permalinks would be “new-cat/foo-category/postname”. So I guess that I could use a permalink as “/%category%/%child-category%/%postname%/ and install Advanced Permalinks to keep the old structure with /%child-category%/%postname%/

So my question is, is there some sort of “%child-category%” for permalink structures?

Thanks,
Combus