Defaulting notice period based calculations on Resignations page

Summary: We have a requirement where we need to default certain calculations on workrelationship DFFs on the Resignation page. If anybody has worked on similar requirements, can you please share your insights on the same? The auto-complete use cases have already been approved. The requirements are as below:

Notice Period as Per Policy: Defaulting the Notice Period value from the Assignment page.

Notice Period Served: Calculating the difference between the Resignation Notification Date and the Resignation Date on the resignation page.

Shortfall in Notice Period: Calculating the difference between the Notice Period as Per Policy and the Notice Period Served.