dictionary sub-value lookup

[Richard]

Hi

I am kinda new to this whole object orientation thing, so
there is probably an easy way of doing this, but the
tutorials etc are sparse.

I have an object M which contains N dictionaries. Inside
dictionary N, is an identifier, Y, plus various other
values, eg: Z.... is it possible to find M.Y.Z without
looping through the whole of M, checking Y each time ?

Since I will have to do a LOT of this, and M may be large,
I need a fast method.  

Ideas/comments etc ?

-Bye
-Richard