Companies and Company Codes

Hi, I have a question related to Company and Company Code cocept in CLM 9.0

I create three companies in my Dev system and import six Company Codes from ERP.

When I create a user it is mandatory to link the user with a Company, and in the Security Tab I add all of the Companies in the system.

Then I start Master Agreement creation but I cannot change the field "Company" and also I have no field to enter the ERP Company Code then I think that I have some concept wrong related to this topic.

The business requirement is that a user may create a Contract for any Company Code defined in the system. Is it possible in CLM?

Thank you!

Celeste