RangeSum on Specific Rows

[uko223]

How can I create an expression that range sums on every 7 rows. For example, I am trying to get the table to sum the total of each week and then reset. For column CY WTD Currently, the expression I am using sums the total of all the weeks. 

if([Fiscal - Flag Current PTD]='Y',
RangeSum(Above(
TOTAL
Column(1),0, RowNo(TOTAL)))))

I just need this expression to only rangesum 7 rows up.