Bookmark Hierarchy - InDesign Book

Hi All,

We have InDesign book files which are having Sections/Parts. All the book components are in seperate file and each of the having bookmarks. Is this possible to move chapter bookmarks to Sections/Parts to maintain hierarchy?

Part 1     <Seperate file in Book>

     Chapter 1     <Seperate file in Book>

          Head 1

               Head 2

     Chapter 2     <Seperate file in Book>

          Head 1

               Head 2

Part 2     <Seperate file in Book>

     Chapter 3     <Seperate file in Book>

          Head 1

               Head 2

Thanks

SASEKUMAR