Power Pivot :: How To Calculate Discount In Analysis

I have a problem with calculating discount in PowerPivot analysis. I have

dCalendar , dDiscount, fSalesBook .

dDiscount columns:
DiscKey, StartDate, EndDate, Product, DiscountName, DiscountPercent

fSalebook columns:
OrderDate, Product, Qty, Sales, Discount

dCalendar columns:
Date, Holiday, MonthNo, MonthName, QuarterNo, QrtName, Year.

The problem (at least I feel) is I defined some dates in the Startdate and Enddate for a particular year. But these discounts should apply for all of the years in my fSalesBook, not just for that year in the dDiscount table.

So in essence, when you calculate discount for a product in fSalesBook you should consider only the month and day of the transaction, if the sale is in between the discount dates.

I have the following relationships.

Table [Column] ------->Table [Column]
fSalesBook[OrderDate] -----> dCalendar[Date]

I am not sure how to relate the dDiscount table with the dCalendar table and not sure even there is a need to relate them to calculate Row level discount in fSalesBook. You can change the relations/model if there is need be.

PS: One more clause, Sometimes I offer discount only for a particular product in that Discount season, that's why there is a column for Product in the dDiscount table.

What should be my DAX formula to calculate Row level discount in fSalesBook?

Here is the link for the sample workbook.

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