bill_s1416 wrote...
....
On the summary sheet where I will place this this sumproduct formula in
cell B10. I have in cells B1:B4 the values I am looking for that I can
change and the formula in cell B10 should then update:
B1 = Brand in question
B2 = Territory in question
B3 = Product in question
B4 = # of sales months to sum.

B4 is a wrinkle because the # of columns of data for the sumproduct
formula to sum is variable.
....

=SUMPRODUCT((Data!$A$29:$A$65536=$B$1)*(Data!$B$29 :$B$65536=$B$2)
*(Data!$C$29:$C$65536=$B$3)*Data!$D$29:INDEX(Data! $D$65536:$AA$65536,$B$4))

where Data is a placeholder for the actual name of the worksheet
containing your sales data. Reduce the 65536 instances to the actual
extent of your data in terms of rows. Smaller ranges will recalc
quicker.