Information Screen Header PA20

Hi.

I am configuring the Screen Header for display the name of Boss in the t.code PA20 . With the following step by step the system work fine. And show the name of the Boss using the fields (MANAGERN & OMNGR_NA) . The system show boss using the relationship A012.

For this I am using the path:

SAP Customizing Implementation Guide-->Personnel Management-->Personnel Administration-->Customizing User Interfaces-->Change Screen Header

My question is: How can I create a configuration for get the Boss using other relationship ? or How can modify this behavior?

Regards