Blocks

good evening everybody
i need some help to understand some basics if you dont mind..

i want to know what steps should i follow to make some blocks appear and the
ones that i dont want in a page disappear?

here is what i am confused about...

lets say i have an HTML block in the main page(front page)..this block
contains a link to another page (new.php) , in this (new.php) page i want
some blocks which were not in the index to appear in this new page and
others that were there to disappear..

to accomplish this i worked like this:

i took the (HTML Block) context_id in the (front page) lets say it was =63
and the context_id of the block "A" that i want it to APPEAR in the new.php
page lets sa it was = 64

and in the mdl_context table i inserted this path for the context_id=64 (the
context_id of the block "A" that i want to show in new.php)

/1/2/63/64

i thought this path means: dont show the context 64 unless it comes after
context 63 ,but nothing has changed i still find block "A" every where..

can u plz tell me whats wrong or what am i missing??

thanx alot