update field in Form A after change of field.status in Form B

update field in Form A after change of field.status in Form B

Developing simple tool for Vacation scheduler.

Form A (Employee) has a field "vacation days taken".
Form B (Vacation Request) has a field "vacation  days requested".

When request is 'approved' in the Vacation_Request report (I've added button), and status of the request changed to "Approved"... how can I update the field "vacations days taken"?

Let's say I had 4 days of vacation taken before... Requested 10, request was approved (status changed)... vacation taken shall be updated to 14 days...

I'm completely new to Zoho, and practicing my zero-skills )))