Visual LISP, AutoLISP and General Customization

[#1]

something like below:
level 1 block consists of
level 2 block y1
level 2 block y2
level 3 block z1
level 3 block z2
level 2 block y3
what kind of algorithm should i use? i'm kind of lost in lisp coding, need a clear hint from you guys, many thanks!

[#2]

to be more specific, only one instance of level 1 block existed in drawing, which cannot be selected using (setq ss (ssget "x" (list (cons 0 "insert") (cons 66 1)))), but it's OK if using (setq ss (ssget "x" (list (cons 0 "insert"))))

[#3]

If the block does not have any attributes it can't be selected with the (cons 66 1)

have you tried using "nentsel" refer to the acad help.
B

[#4]

thanks B.
better not have any user selections, i find the way out, use (tblobjname "block" blockname) instead of (tblsearch "block" blockname), the only thing now is to make recursive subroutine to step through nesting blocks no matter how deep it is.