[AccessD] A2K2: Hook into Exchange Address Book

I work for a sizable company (~18,000?).  We utilize an exchange field
called alias to hold the userID of employees.  What is the most efficient
method of validating data entry against a linked  exchange address book?

As a test I tried running a simple query, 4 fields, with my last name set as
the criteria.  It was unacceptably slow, verging on the assumption that
Access had "locked-up".  A ctrl+break stopped the loop but the query had
actually returned the single record.  How can I speed this up?

TIA,

Mark