Function using autofill and auto select - elementary arithmetic

[Kidu]

Hey all
Which function can auto select cells and using the result ,It's pretty complicated to explain so I attaching a file.

For example:

I want to the:
1.Result of all the remainder (increment) between the open and close columns of each day (display it some column)
2.Multiple it by some number and add it to next day open column and then the all process again... (each day it imports the remainder (only) again)




Thanks in advance.
Kidu