Dont know of way to do what your asking, but there is a way to get your personal contacts with the exchange contacts.
I took all of my personal contacts and emailed them to my work email.
Added the contacts under a personal folder under my exchange account.
Now on the ipone, i have my personal group as well as the corporate directory. Any new contacts, i can add at work and email home, or vice versa.
not the best solution, but works for me.