reverse proxy in apache with ldap

Hy people i have a question!,

what i have right now is:

internet----------------------apache-reverse-proxy----------SPS servers
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|
AD free domain

the proxy has authtype basic and looks for the user with ldap in and windows AD domain, what i need now is that the reverse proxy can validate users from several domains not only 1 as it does now, does anybody now how you can make the auth_ldap mod connect to several AD servers to validate a user?

So i could have something like:

AD second domain
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internet----------------------apache-reverse-proxy----------SPS servers
| |
| |
AD free domain |
AD third domain

the reverse proxy has this proxy configuration:

AuthAuthoritative Off

AuthName "Staff only"

AuthType Basic

LDAP_Debug On

LDAP_Server 172.

LDAP_Port 389

Base_DN ""

Bind_DN ""

Bind_Pass ""

UID_Attr cn

require valid-user

</Proxy>

reverse proxy in apache with ldap_auth mod