Security at dashboard level vs workspace

Hi all,

Is it possible to set roles/security for users at the dashboard level within a workspace?

e.g., a finance dashboards workspace that contains 5 reports, 1 of which contains highly sensitive data that contains its own level of security loosely associated with the workspace security (i.e., users will require access to this dashboard to get into it).

OR is it possible to nest workspaces within workspaces (e.g., user requires both workspace security access to both workspace to access the nested workspace).

Thanks,

Mork