Are there any shared service customers who have managed to segregate users to not appear in LOV's?

Summary: We have a requirement whereby a shared service managed system has employees and shared service users who need to be segregated so that only the actual employees show up in any LOV

Content (required): As per the above summary, we have a requirement whereby a joint venture has a workforce of employees and some shared service employees. The shared service employees cannot be on any LOV such as delegations for expenses or attendees for meals. They need to be segregated from any LOV and just be there for more of a maintenance/ management role. The only users seen in any LOV will be the actual employees of the main company.