Connecting Open Directory to Active Directory

Hello

We have 2 offices in different cities.
One Office is complete Windows based and has 2 AD Server and 2 Citrix Server in a Farm
In the other office we have only Mac connecting to an OD Server. All this user using Citrix Dazzle to connect to the server in the Head Office

Now we want wo share the information of the AD to the OD server this because it is frustrating to add new personal on 2 server seperate.

How is it possible to migrate those 2 AD & OD server, so a user can be create on the AD and will be automaticly availible on the OD Server to logon OD Worksatation on the secong office

Gerard