Department and Function fields in customer and vendor master data

Hi,

I am new to ABAP and work as FI consultant. I have got two requirements which are not possible to be done in customizing;

• Specific Department and Function fields in customer and vendor master data should set as Mandatory,
• Corresponding to this specific Department and Function field, I have to set a control in telephone, fax and e-mail fields which cannot be created/changed master data in XK01-02, XD01-02 etc.

How can I achieve these functionalities?

Thanks in advance,