Table design problem

[SD]

Hi,
I have got 3 tables one stores Storeid,product,week#,sales,returns
another contains Storeid,product,month#,sales
Month_todate,returns_month_to_date and last one contains
Storeid,product,quarter#,sales_quarter_to_date,ret urns_quarter_to_date

I want to produce a report that has the following output for SALES,
RETURNS
current_WeeK,Month_to_date,quarter_to_date,
LastYR_Same_Week,LastYR_Same_month, LastYR_same_quarter, DIFF(
Week-LAST_YR_SAME_week) Percentage INC/DEC etc..)

What is the most optimum way to design for this requirement

Since I would like to use Excel as the Front end for report does it
make sense to put the data in a Pivot format. If so then what should
the design be?

any thoughts would help

Thanks