How to expand only one level of nested objects?

Hi,

I have a nested object hierarchy e.g.

A.B.C.D

Where each level might be an object or an expandable collection.

i)

I would like to show the selected object and then allow just one level below this to be expandable. Anything deeper that one level below the selected object should be hidden. I want to be able to set any of A, B, C or D as the selected object and still have just one level belwo the chosen object as expandable.

With different selected objects, this would mean the user would see e.g.

A
|--B

and

B
|--C

and

C
|--D


ii)

Could I control the depth of visible expandable objects at run-time?

thanks,
Duncan

[Modified at 08/12/2011 10:55 AM]

[Modified at 08/12/2011 10:59 AM]