calculating seniority banking

[Anonymous]

I have table Fact_an

Code_produit	Code_Gestionnaire_Prod	ID_DateFicheAgent	NBAN	Ref_Id	banking seniority
1253	12356	04/01/2020	200	1	1
8596	9658965	05/01/2020	600	2	1
25863	963258	06/01/2020	1800	3	2
25632	12356	07/01/2020	5400	4	2
1253	9658965	08/01/2020	16200	5	2
8596	963258	09/01/2020	48600	1	5
25863	12356	10/01/2020	145800	3	5
25632	9658965	11/01/2020	437400	4	3
1253	12356	04/01/2019	123	1	8
8596	9658965	05/01/2019	600	2	8
25863	963258	06/01/2019	1800	3	8
25632	12356	07/01/2019	600	4	8
1253	9658965	08/01/2019	600	5	7
8596	963258	09/01/2019	600	1	7
25863	12356	10/01/2019	600	3	7
25632	9658965	11/01/2019	600	4	7

banking seniority

banking seniority	Name
1	less than 1 year
2	less than 2 year
3	less than 3 year
4	less than 4 year
5	less than 5 year
6	less than 6 year
7	less than 7 year
8	less than 8 year

I create a report and a new mausure AN. WHE A USER SELECT A YEAR AND A MONTH AND banking seniority, I need to calculate the count of the rows the last 12 of months banking seniority< banking seniority seelcted by the user

AN = 

VAR a = SELECTEDVALUE(Dim_DateFicheAgent[ID_DateFicheAgent])
VAR b =SELECTEDVALUE('Seniority banking'[banking seniority])
RETURN

    CALCULATE (
COUNTROWS(FILTER(Fact_AN;

     (Fact_AN[banking seniority]<=b && NOT ISBLANK (Fact_AN[banking seniority]))));
         DATESBETWEEN (
        Dim_DateFicheAgent[ID_DateFicheAgent];
        NEXTDAY ( SAMEPERIODLASTYEAR (LASTDATE ( Dim_DateFicheAgent[ID_DateFicheAgent] ) ));
        LASTDATE ( Dim_DateFicheAgent[ID_DateFicheAgent] )

))

it returns errors wrong values. I put an example of the report here https://drive.google.com/file/d/1Ja3NevOm6i80uuS6lKPpHIBYaNQ2jee2/view?usp=drivesdk

[v-chuncz-msft]

@Anonymous 

See solution in post below.

https://community.powerbi.com/t5/Desktop/calculating-seniority-banking/m-p/1078783