You can use this formula in cell B3 of the Mastersheet:
=SUM(C3:K3)
Copy down to the bottom of your table, then you can copy all those formulae across into the other Cumulative columns.
In the Frontsheet you can use this formula in cell C3:
=IFERROR(INDEX(Mastersheet!$B$3:$CC$5,MATCH($A3,Mastersheet!$A$3:$A$5,0),MATCH($B$1,Mastersheet!$C$2:$K$2,0)+MATCH(C$1,Mastersheet!$B$1:$CC$1,0)),"")
and this one in D3:
=IFERROR(INDEX(Mastersheet!$B$3:$CC$5,MATCH($A3,Mastersheet!$A$3:$A$5,0),MATCH(C$1,Mastersheet!$B$1:$CC$1,0)),"")
Copy those two formulae down to the bottom of your table, then you can copy that block of formulae across into the next pair of columns, and repeat.
Hope this helps.
Pete
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