Hi
Can you please check the tables USRM1, USRMM
These tables have Userid and Company code relations..
Or
From PA0001 table and you can find the Personnel numbers (Pernr) by company code. From the Pernr you can find the user id from infotype PA0105.
PS: (From USRM1 table .... you can get atleast plant (werks) of the User.. From plant you can get the company code)
Regards,
Venkat