Book Chapter and Section Numbering

Hi,

I've been through the tutorials and cannot seem to find a solution to my problem. Maybe I'm missing something simple here. Basically, I'm writing a book and want each chapter in a separate document with contiguous section numbering. e.g.

Document 1.

Chapter 1

   Section 1.1

       Section 1.1.1

       Section 1.1.2

            Section 1.1.2.1

   Section 1.2

       Section 1.2.1

       Section 1.2.2

Document 2.

Chapter 2

   Section 2.1

       Section 2.1.1

       Section 2.1.2

            Section 2.1.2.1

   Section 2.2

       Section 2.2.1

       Section 2.2.2

If I define the Chapter as a Section heading with a level 1 hierarchy and each sub-section with level 2, 3, 4, etc hierarchy, the above works fine within each document, but section numbering always stays at 1 in each document and doesn't increment when I make the book i.e all chapters remain at Chapter 1 within each document.

If I use the Chapter text variable, chapter numbering updates, but the section numbering isn't linked to the chapter number e.g. Section 2.1 in document 2 now becomes Section 0.1, since there is now no level 1 Section heading defined.

Please help,

Thanks.