Here is a formula that is working, but would like to modify.

=IF(F89="","",SUMPRODUCT(('Sheet1'!$C$6:$C$251=F89)*('Sheet1'!$K$6:$K$251)))

I have a list that goes from K6:K3600; however, currently my data only goes to row 251.
If I change my reference to 3600 I get an #Value error, because the data from row 252 to 3600 is still empty.

Is it possible to modify the formula in order to make the reference relative instead of absolute? To clarify, if I add information to my list (row 252), that my formula automatically changes to 252 instead of staying at 251 reference.

I tried this formula without success...
=IF(F89="","",SUMPRODUCT(('Sheet1'!$C$6:$C$row(B2)=F89)*('Sheet1'!$K$6:$K$row(B2))))
whereas row(B2) is a MAX formula returning the row number of the last cell that has information; in this case 251.