I'm trying to adapt the excellent answer above, but simplify it in 2 ways:

I have my data across a row, so swapping row() to column() and removing transpose()...

and

i'm after a simple cumulative of ALL the numbers in the row, (rather than needing the sumif condition of column B:B's "item A" that the original poster had...

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I have dates to index in $K$7:$7, and expenditure data across $K14:14, and need to find the date in row 7 that the cumulative expenditure in row 14 reaches 10% of the row 14's total in $G14

i'm trying this but it's not working for me...

=INDEX($K$7:$7, MATCH(TRUE, SUMIF(OFFSET(B2,0,0,column($K14:14)-column($K14)),"A", OFFSET(C2,0,0,column($K14:14)-column($K14)))>=0.1*$G14, 0))

Thanks in advance