Custom Fields in Header for FB70

[spartans007]

Hello,

I have a requirement to add Custom ZZ Fields to transaction FB70 in the Header Section. Please guide me through the Following:

The Custom fields should have the ability to Save, Park and Post.

For this requirement what are the Tables required that I need to Append Structure with the custom ZZ fields?

Which Screen Exit required to add the custom fields and where to add the Custom Code?

Also can some one please provide me the code too which is required to SAVE, PARK and POST these custom ZZ fields in FB70.

Thank You.