Appendix Section numbering

I am using InDesign CS6, I would like to create numbering in an Appendix section, like this:

A1.

A1.1

A1.2

A1.1.1

A1.1.2

A1.1.1.1

A1.1.1.2

A2.

A2.1

A2.2

A2.2.1

A2.2.2

A2.2.2.1

A2.2.2.2

Can anyone tell me how to go about this please?  Thank you.