Taxonomy and cck fields. If I pick one taxonomy term, can I use that term to narrow down my options in a related CCK Field?

I have a really complicated document library to set up and I'm not sure what to do because I'm stuck.
I have a complicated document series to manage. Each document belongs to a top tier category and then with in that they belong to a smaller category. So Like a document, could be part of the Networking category but within that belong to standards.
So, i put the top tier categories in to a taxonomy term field and put the mini-child categories into a CCK Select field. So a user will pick the top tier category and pick the sub category. This is because I'm going to use Views and Views accordion to make each node group by top tier category and then there will be smaller views pages that group by sub category.

My question is: If I pick one taxonomy term, can I get the CCK field following it to narrow it's choices down automatically to the categories that fit the taxonomy term?

Here is an example of what I mean, which might be more concrete :

TOP LEVEL TERM -->Overall Deployment, Applications and OAM

Mini_categories-->Reserved
Multiple-cross technical requirements
Credentials
Application level studies
Spectrum policies studies

Picking a top level term narrows down the mini categories automatically.

If i have to re-do the CCK field to something else, I don't mind. I tried doing research about this on the site but couldn't find anything good or that is what I mean.

Becky