HOW can I calculate a weighted quartile/IQR? in excel?

Hi all. I have the following data :

Column A is the value (0, 1, 2,,, 255) :: A1~A256
Column B is the amount of each value :: B1~B256

I want to calculate the weighte quartile and IQR of the value of column A, weighted by column B(the amount of each values)..

I've tried the quartile function, and it doesn't seem to work.

This function is resulting to the #NUM! error :
= QUARTILE.EXC(SUMPRODUCT(A2:A256,B2:B256)/SUM(B2:B256),1)
= QUARTILE.EXC(SUMPRODUCT(A2:A256,B2:B256)/SUM(B2:B256),3)

And this function is resulting to the weighted average :
= QUARTILE.EXC(SUMPRODUCT(A2:A256,B2:B256)/SUM(B2:B256),2)

I can do a quartile of one column and a weighted average of 2 columns.. but am unable to calculate a weighted quartile, median of 2 columns...

PLEASE HELP !!!!

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