[Exim] LDAP lookups

We have a complex LDAP structure, I've been though the examples and I am
still stuck.

What happens is we have a LDAP group, for instance - where cn=mis.
Then we have users who's memberOfGroup attribute equals the dn of the
group.

So if someone sends email to mis@??? I need exim to do this
lookup
query =
ldap://ldap.doc.state.vt.us/cn=${quote_ldap:$local_part},o=Vermont%20Department%20of%20Corrections,c=US?dn?sub?

(hoping this is going to search the different branches in our ldap for
cn=mis and return a dn, now with this found dn I need to do a second
lookup)

the second lookup is to use that dn to search for memberOfGroup=dn.
Im guessing something like this:
query =
ldap://ldap.doc.state.vt.us/memberOfGroup=$quote_ldap:$local_part},o=Vermont%20Department%20of%20Corrections,c=US?mail?sub?

(Hoping that this will finally get a bunch of users mail addresses.

Please let me know how I can do this. And also clue me in on what
$quote_ldap is?
Thanks,
Joe Kezar
Vermont Department of Corrections
jkezar@???