[Excel Hater]

I have filters on and I'm using the SUM to add a group of numbers. It seems
that excel automatically adds adjacent cells that I have hidden(I'm guessing
it's adding the hidden cells cause the result is way off and I get a formula
error however; the formula does not reflect these additional cells). I have
unselected the extend data range option, but this only works the first time.
After I start working on the spreadsheet and add more SUM formulas it reverts
back to adding the hidden cells.

I have thousand of numbers so it's not efficient to select each one
individually and I don't remember having to do that before. I used to be
able to use the shift key while selecting large data ranges without it
selecting hidden cells in between.

Is there a way I can permanently disable Excel from automatically including
adjacent cells when using SUM?