Hello Maria,
How do you define who's the secretary of a given employee? Do you have any relationship in OM for instance? If yes, you can define an evaluation path (transaction OOAW) which starts from a secretary and retrieves all employees in his/her range of responsibility. Then, define an object rule selection in OADP with this evaluation path, and put this rule in an object selection and then in your org view group.
I suggest you start by reading the OADP documentation: http://help.sap.com/erp2005_ehp_06/helpdata/en/e7/947e40ec66ce62e10000000a155106/content.htm
Regards,
Julien