using a calculated date field in another calculated measure

I have a table containing the Opportunities and Stage

I added a date column

NewDate = Date(Year(Opportunity[Close Date]),month(Opportunity[Close Date]),01)

Added a measure to compute min of  NewDate based on a filter

MinETCDate = CALCULATE(Min(Opportunity[NewDate]),Opportunity[StageNo]<> 0)

Added a meaure to compute maximum of NewDate based on a filter

MaxETCDate = CALCULATE(Max(Opportunity[NewDate]),Opportunity[StageNo]<> 0)

Computed the months in difference using 

MonthDiff = DATEDIFF([MinETCDate],[MaxETCDate],MONTH)

I have a measure of TotalWonValue defined as

TotalWonValue = CALCULATE( sum('Opportunity Details'[Total Price]),Opportunity[Opportunity Stage]="Closed - Won")

So far so good.

Now I want to find the TotalWonValue in the months provided by MonthDiff prior to the MinETCDate.   

I tried various combinations but with no success.

Any help would be appreciated.

Cheenu Sing

Upto this is fine.