Using macro to distribute task evenly

Hi, I've this template that is used to distribute task evenly amont all staff. Each day there will be a different amount of files coming in ranging from 10 - 35. The file needs to be divided among 5 staffs daily. Is it possible to use a macro to automate it? Such that it will have a input box to prompt user to key in the amount of file for the day and it will split evenly. Below is the template that I've been using. The yellow shading means where the routing starts from. The x means the particular staff is on leave. How the routing starts from is based on the previous day if there is any remainder. Eg if A - D do 5 and E do 4, the routing will start from E the next day. Please see attached file for info

Or is there a better solution to it?
Thanks!