Modify existing formula to only include results based on a date range (month)

[Badvgood]

I am looking to modify this formula so it only counts the values for an individual month as opposed to counting all of the results.

=IFERROR(ROWS(UNIQUE(FILTER('gsp Rolling 12'!$Z$2:$Z$150000,'gsp Rolling 12'!$C$2:$C$150000))),)

Formula to go in sheet gsp Output by Month, E2

Manual calculations are entered into the cells to show what I would expect.

Could anyone assist me please?

Thanks BVG

[Fluff13]

How about

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[Bo_Ry]

Please try

=MMULT(--TRANSPOSE('gsp Rolling 12'!C2:X20),--(MONTH('gsp Rolling 12'!A2:A20)=SEQUENCE(,12)))

[Badvgood]

Worked perfectly, that you once again Fluff13

[Badvgood]

Sadly, this did not give the results expected when working with large amounts of data. Thank you for assisting.

[Fluff13]

Glad to help & thanks for the feedback.