8 weeks data based on user input

HI Experts,

We have a requirement to display the graph as below format based on user entered date .ie "Start Date " and "End Date":

We have from and to date as input from user: "Start Date" and "End Date"

We need to display last 8 weeks data from the End date and display the count of "Spend Error" in the body of Graph in the same format as shown above. ok,we have date as below.

we have created two formula it is giving total count of 8 weeks.

Var1

=RelativeDate((ToDate(UserResponse("Spend End Date");""));-55)------->this start date of the first week

Var2:

V_Graph_Spnd_End Date_8Weeks

=LastDayOfWeek(ToDate(UserResponse("Spend End Date");""))---------->this will give end of 8th week

var3:

=Count([Spend].[Err Cd Id]) Where ([Spend].[Transaction Dt] Between( [Var1];[Var2]))---->this will count of total error but we need for last weeks from end date.  Please guide me