Order different fields as items of one list

Hello!

I have custom style, and I want to sort bibliography items depending on Author and Title. Ofcourse I can do  in Bibiliograpfy-> Sort Order:

Author +
Title

But in this case itesm with empty Authors apear first in the list.whose  Author OR Title. E.g. if I have author whose name starts with letter ‘A’ and bibliography item which has no Authors, but Title starts with ‘B’, I want them to be sorted as:

1. A... (with author)
2. B... (only title)

Thank You again!!! I was afraid that no one would answer that question, therefor I posted it here under another topic.