I am using MS Office 2007. I am preparing a report which contains several chapters and sub chapters. I want the report in the following format.

1. CHAPTER TITLE
1.1 Sub Chapter
1.2 Sub Chapter
1.2.1 Sub- Sub Chapter
1.3 Sub - Chapter

2. CHAPTER TITLE
2.1 Sub Chapter

. , , ,


and so on.

But as I am preparing the document. After finishing the finishing the first chapter, the numbering is coming like this.

1. CHAPTER TITLE
1.1 Sub Chapter
1.2 Sub Chapter
1.2.1 Sub- Sub Chapter
1.3 Sub - Chapter

2. CHAPTER TITLE
1.4 Sub Chapter
1.5 Sub CHapter
1.5.1 Sub - Sub Chapter..

and so on.

Please Help me how to solve this.

Thankyou in advance.