Numbering

[Joseph Hesse]

My lyx document is a book with chapters in a master document.  I add 
computer program listings, from files in other folders, with 
Insert->File->Child Document->Program Listing.  This works well for me.

The numbering of the program listings is 2.1, 2.2, 2.3, etc. where the 2 
is the chapter and the number after the dot is a counter that keeps 
incrementing after a new listing is added.  I would like to change this 
so the numbering is Chapter.Section.Counter e.g. 2.2.1, 2.2.2, 2.2.3  
where these are listings in chapter 2, section 2.

How do I do this?  Please point me to a package that will help me 
implement this.

Thank you,
Joe