Delegating group administration within a domain (permissions problem)

I have a situation where I want a set of administrators to add/remove
computers to global groups within AD (used for Sofware distribution).
I only want them to be able to add/remove computers from these groups
if they are computers within their region. I can restrict their right
to add computers but I am having difficulty restricting their right to
see/remove only the computers that they administer. The groups for
software distrubition are centrally located and I don't want to have
to create new groups for each region and nest them inside the central
groups.

Thanks in advance,

Russell