Which sample? What about them aren't exactly what you're looking for?
Can you attach sample data so that we can help you?
For Current week value you can create calculated field as "Current week=now()" which will give you current week number and this field can be used as a default filter in your work sheets.
But to help you exactly what you need plz attach your work book with dummy data.
I have attached a sample I found here in the forum (couldn't find the original discussion).
Now, as far as I understood, it does calculate the current period vs. previous and also the delta.
But, if I implement the same on my data, and use a field calculated as a percent, I get incorrect numbers.
The percentage is not being calculated correctly per period.