Rolling SUM as DAX measure

[hobeee]

I am trying to SUM my SALES_AMT for the last 12 months as a rolling amount IF there is an entry OR NOT equal to "" (blank).
I am not sure how to correctly write the filter. Below I give an example.

=CALCULATE(sum(FSales[SALES_AMT]), DATESBETWEEN(DateTable[DateKey],FIRSTDATE(PARALLELPERIOD(DateTable[DateKey],-11,month)),lastDATE(PARALLELPERIOD(DateTable[DateKey],0,month))))


I have the relationship between the FSales and Datetable as many (date) to one (date).
I want my powerpivottable to read :

2014	January	1 or more period w/o sales
2014	February	1 or more period w/o sales
2014	March	1351.5
2014	April	1258.4
2014	May	1234.6
2014	June	1324.3

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FSales table :

1/1/2013	61.9
1/15/2013	10.1
1/29/2013	53.1
2/12/2013	35.6
2/26/2013	69.4
3/12/2013
3/26/2013	21.3
4/9/2013	87.9
4/23/2013	25.1
5/7/2013	55.0
5/21/2013	76.6
6/4/2013	34.5
6/18/2013	10.1
7/2/2013	71.8
7/16/2013	86.9
7/30/2013	38.4
8/13/2013	63.9
8/27/2013	62.3
9/10/2013	38.2
9/24/2013	80.4
10/8/2013	55.6
10/22/2013	28.5
11/5/2013	47.2
11/19/2013	64.3
12/3/2013	50.3
12/17/2013	10.1
12/31/2013	60.2
1/14/2014	48.2
1/28/2014	50.2
2/11/2014	22.2
2/25/2014	78.5
3/11/2014	10.8
3/25/2014	94.6
4/8/2014	1.9
4/22/2014	18.1
5/6/2014	49.2
5/20/2014	58.5
6/3/2014	45.5
6/17/2014	78.7

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[scottsen]

Your formula read pretty well to me. It's unclear what problem you are having?

This article may help? Rolling 12 Months Average in DAX | SQLBI