Mapping AD groups to BO groups - AD plugin CMC

Hi,

Im configuring SSO, before that i have to map groups and sub groups with same groups/sub groups in BO.

Example :

AD Level                                 CMC

[ROOT/OU] - bo users

1.Finance    -->                    1.  Finance

2.HR           --->                         2.HR

    2.1 Training dep                     2.1 Training dep     

Requirement --> ONE TIME CREATING GROUPS./ SUB-GROUPS AND MAPPING TO GROUPS IN CMC. So the admin team next time add/eidt/delete any users in AD, it should automatically reflect in BO[currently using "+update" plug in option in CMC]

My requirement is I need to map groups in AD with groups in BO along with any sub groups. How do I achieve it? Another related query is there are existing groups in BO which i need to map too. How do i map existing groups with the groups in AD which is going to be created now with same names. Is there any way i can merge existing groups on BO with same group in AD. I tried adding the users from existing groups to group which I added though plugin[same name], i get an error saying "cannot add users to third party group"

Please guide me.

TIA.