how to create the PRODUIT function in DAX

[TransfoBart]

Dear all,

I have been tasked to create a PowerBI dashboard, in which there is a portfolio of holdings. All fine, but one requirement: calibrate the portfolio every 15 days.  I figured all out in Excel, and came quite far in PowerBI DAX. That is: up to the column "cumul calibration" as shown below.  In excel it´s a plain PRODUCT function, but I have no clue how to do this in DAX.

Would be great if anyone can help me out,

cheers

[TransfoBart]

Dear Daniel, I would like to use this as a measure: the values in the [calibration per 15 days] are coming from a measure. However, if I do that, I am missing the row context; "EARLIER refers to an earlier row context which doesn´t exist".  Any ways around this?

[TransfoBart]

merci beaucoup Daniel!  Works beautifully...

[wdx223_Daniel]

NewColun=PRODUCTX(FILTER(Table,Table[Date]<=EARLIER(Table[Date])),Table[calibration per 15 days])