Need to CALCULATE Subscriptions Retained Between Start and End Date

[kbirstein]

Hi, I have data for subscriptions purchased per week and am trying to show the retention as weeks progress. The data looks like this:[TABLE="width: 500"]
<tbody>[TR]
[TD]SubID[/TD]
[TD]SubBeginWeek[/TD]
[TD]SubEndWeek[/TD]
[/TR]
[TR]
[TD]1000ADW[/TD]
[TD]12/30/2012[/TD]
[TD]2/13/2013[/TD]
[/TR]
[TR]
[TD]2599BRG[/TD]
[TD]1/20/2013[/TD]
[TD]2/24/2013[/TD]
[/TR]
[TR]
[TD]3800ADC[/TD]
[TD]2/17/2013[/TD]
[TD]3/17/2013[/TD]
[/TR]
[TR]
[TD]9809IUO[/TD]
[TD]12/30/2012[/TD]
[TD]2/10/2013[/TD]
[/TR]
</tbody>[/TABLE]

etc. I have created a simple PowerPivot table with the rows being SubBeginWeek and the columns SubEndWeek and with COUNTA(SubID) as the value. This gives me a PowerPivot that looks like this:

[TABLE="width: 500"]
<tbody>[TR]
[TD][/TD]
[TD]12/30/2012[/TD]
[TD]1//6/2012[/TD]
[TD]1/13/2012[/TD]
[TD]1/20/2012[/TD]
[TD]1/27/2012[/TD]
[TD]etc.[/TD]
[/TR]
[TR]
[TD]12/30/2012[/TD]
[TD]2053[/TD]
[TD]1727[/TD]
[TD]996[/TD]
[TD]897[/TD]
[TD]1998[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]1/6/2012[/TD]
[TD][/TD]
[TD]1536[/TD]
[TD]789[/TD]
[TD]954[/TD]
[TD]1024[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]1/13/2012[/TD]
[TD][/TD]
[TD][/TD]
[TD]1345[/TD]
[TD]768[/TD]
[TD]887[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]1/20/2012[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD]879[/TD]
[TD]1879[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]1/27/2012[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD]1888[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]etc.[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]

which is telling me how many subscribers CANCELLED in each week (i.e., for those who signed up in the week of 12/30/2012, 2053 cancelled the first week, 1727 cancelled the second week, etc.). However, what I want to show is how many REMAINED in each week.

Is it possible to create a measure with CALCULATE with ALL that will give me the values I want (i.e., all those who signed up in the week minus those who cancelled)?

Any help greatly appreciated!

Kathryn