Users in a department and users in a company code

Hi,

1) If I have a department name (as maintained in attributes in TCode ppoma_bbp) how do I find out all the users in that department.

2) If I have company codes how do I find out all the users in those company codes

We are using SRM 4 extended classic scenario.

Are there any function modules or tables that can give me the answers?

Thanks and Regards,

Mick