GAL Merger using LDAP

How can I automate and remotely setup an address book entry in Outlook 2007 to use a LDAP entry by using a .reg or .bat file?
I have manually done my addition but need to do this to a large number of users. I located the registry changes needed to modify the settings for each user but cannot see the address book entry once the .reg file successfully runs when the users reopens outlook . I would like to have this modification happen when users logon onto the domain. No LDAP server is in place or plans to install one. 3rd party apps are not to be used unless approved. Thanks in advance for those willing to help.