ldap search to find dn for user

How can I do a ldapsearch to find a DN for a user when I know the exact cn for that user out of active directory.

I have tried several different commands (hundreds) but need the -b with the full dn to perform the search using ldapsearch from AIX. I am trying to find the OU for a user and the sAMAccountName. Our user are in several different OU's.

example that works:
ldapsearch -h something.acorp.com -p 389 -D "cn=${USER},ou=RealOU,DC=something,DC=acorp,DC=com" -w "${PW}" -s sub -b "cn=${SEARCH_USER},ou=UsersRealOU,DC
=something,DC=acorp,DC=com" "cn=*"

example that does not work (one of many):
ldapsearch -h something.acorp.com -p 389 -D "cn=${USER},ou=RealOU,DC=something,DC=acorp,DC=com" -w "${PW}" -s sub "cn=${SEARCH_USER}"

Double post, continued here, thread closed.