Trailing 12 week cash balance line graph

Hi,

I am accessing QuickBooks Online using the content pack and look to create a WEEKLY, trailing 12 week line graph representing the actual cash balance for each week ( 13 data points -- cash balance on the day of the report and then the cash balance for each of 12 weeks prior (todays date minus 7 days, 14 days, etc).  (Once/if I get this working, I will look to add bar chart with total cash deposits and total cash payments for that same 7 day period).  

What I attempted to do was use the Measures below to calculate the cash balance, this formula worked, but obviously, I can put these Measures into a line chart.  I included a Visual Filter on the specific Cash Account that is the subject of the graph.

T0W Cash = SUM(GeneralLedger[TxnAmount]

T1W Cash = CALCULATE(SUM(GeneralLedger[TxnAmount]), 'GeneralLedger'[Date] <= TODAY()-7)

T2W Cash = CALCULATE(SUM(GeneralLedger[TxnAmount]), 'GeneralLedger'[Date] <= TODAY()-14)

Day of the Report --> T0W

Trailing 1 Week --> T1W

Etc.

Suggestions?