I don't know if this is possible, but I have tried and failed to do the following using sumproduct and sumif(s).
Sum all values in array 'Tabbing Data'!$A$2:$CA$5000
Where column header = a value in a reference matrix, e.g. 'Tabbing Data'!$A$1:$CV$1='Data Gap Check'!$P47
And where 'Data Gap...